Identification and kinetic analysis of a functional homolog of elongation factor 3, YEF3 in Saccharomyces cerevisiae

Yeast and other fungi contain a soluble elongation factor 3 (EF-3) which is required for growth and protein synthesis. EF-3 contains two ABC cassettes, and binds and hydrolyses ATP. We identified a homolog of the YEF3 gene in the Saccharomyces cerevisiae genome database. This gene, designated YEF3B, is 84% identical in protein sequence to YEF3, which we will now refer to as YEF3A. YEF3B is not expressed during growth under laboratory conditions, and thus cannot rescue growth of YEF3A deletion strains. However, YEF3B can take the place of YEF3A in vivo when expressed from the YEF3A or ADH1 promoters. The products of the YEF3A and YEF3B genes, EF-3A and EF-3B, respectively, were expressed from the ADH1 promoter and purified. Both factors possessed basal and ribosomal-stimulated ATPase activity, and had similar affinity for yeast ribosomes (103 to 113 nm). K_m values for ATP were similar, but the K_cat values differed significantly. Ribosome-dependent ATPase activity of EF-3A was more efficient than EF-3B, since the K_cat and K_cat/K_m values for EF-3A were about two-fold higher; however, the difference in K_cat/K_m values between the two factors was small for basal ATPase activity. © 1998 John Wiley & Sons, Ltd.     

Isolation and sequence analysis of the gene encoding translation elongation factor 3 from Candida albicans.

The structural gene encoding translation elongation factor 3 (EF-3) has been cloned from a Candida albicans genomic library by hybridization to a Saccharomyces cerevisiae probe containing the Saccharomyces gene, YEF3 (Sandbaken et al., 1990b). The sequences were shown to be functionally homologous to the Saccharomyces gene by three criteria: (1) a Saccharomyces strain transformed with a high copy plasmid containing CaEF3 sequences overproduces the EF-3 peptide two-fold; (2) extracts from this strain exhibit a two-fold increase in the EF-3-catalysed, ribosome-dependent ATPase activity (Kamath and Chakraburtty, 1988); and (3) the Candida gene complements a Saccharomyces null mutant. The coding region, identified by DNA sequencing, indicates that CaEF3 encodes a 1050 amino acid polypeptide having a potential molecular weight of 116,865 Da. This protein shows 77% overall identity to the Saccharomyces YEF3 gene, with a significantly greater identity (94%) concentrated in the region of the protein thought to contain the catalytic domain of EF-3 (Sandbaken et al., 1990a). The upstream non-coding region contains T-rich regions typical of many yeast genes and several potential RAP1/GRF1 elements shown to regulate expression of a number of translational genes (Mager, 1988). The data confirm a high degree of conservation for EF-3 among the two organisms.     

Cloning and genetic analysis of the gene encoding a new protein kinase in Saccharomyces cerevisiae

We have isolated a single gene from the yeast Saccharomyces cerevisiae encoding a potential 800 amino acid polypeptide of calculated M_r 90 098 Da. This protein consists of an N-terminal region that shares significant homology with the catalytic domains of several serine- and threonine-specific protein kinases, as well as a large, unique, C-terminal domain of unknown function. Haploid disruption mutants are viable and do not exhibit any readily observable growth defects under varying conditions of temperature, nutrients or osmotic strength. Due to the apparent structural similarity between this kinase and the protein products of the KIN1 and KIN2 genes, we have chosen to name this new gene KIN3.     

The subunit structure and stability of conglutin δ, a sulphurrich protein from the seeds of Lupinus angustifolius L.

The oligomeric structure and stability of conglutin δ, the 2S sulphur-rich lupin seed protein, has been studied. Molecular weights were determined by sedimentation equilibrium methods in the analytical ultracentrifuge. Conglutin δ₂ (M_r 14 000, 2S), the most abundant form, was composed of one large (?9600) and one small polypeptide chain linked by disulphide bonds. The minor oligomeric form, conglutin δ₁ (M_r 28 000, 2.8S), was a disulphide-linked dimer of conglutin δ₂. Each form was capable of reversible association and at low ionic strength (neutral pH), the conglutin δ₁ momomer associated to a homogeneous dimer (M_r 56 000, 4.1S). Calculated frictional ratios (f/f₀ ? 1.28–1.49) suggested that the three different forms were asymmetric. Spectral studies (ORD/CD) showed that conglutins δ₁ and δ₂ were rich in alpha-helix (?38%) unlike the major 7S and 11S legume seed storage proteins. The helical structure was unusually stable both to heat and chemical denaturants; below 60°C (at neutral pH) the helix remained unaffected and only partial denaturation occurred at higher temperatures. Nevertheless, complete denaturation was achieved (at 20°C) in high concentrations of guanidine hydrochloride (greater than 6.5 M). The stability was due to the presence of disulphide cross-links; with the addition of reducing agent, as little as 1 M guanidine hydrochloride (GuHCl) was sufficient for denaturation of the helical structure. Titration experiments showed a single buried tyrosine (pK 11.4) which could be exposed (pK 10.2) in 6 M GuHCl.     

Gel filtration studies of peptide metabolism by rumen microorganisms

Peptide metabolism by rumen microorganisms was investigated by gel filtration using Sephadex G-25 with water as eluant. Protein hydrolysates containing a mixture of peptides were used to calibrate the column. Total peptide in each fraction was estimated from its A₂₀₆, and free peptide amino groups were analysed by fluorescamine, thus enabling the average peptide M_r to be calculated. Three different protein hydrolysates produced similar, nearly linear, relations between log M_r and elution volume for peptides between 300 and 2000 Da. Trypticase, a pancreatic hydrolysate of casein, was metabolised rapidly in rumen fluid in vitro. Hydrolysis appeared to be complete after 6 h, leaving a small residual peptide concentration which persisted up to 24 h, equivalent to about 15% of the original peptide concentration of 2 g litre^?1. Residual peptides from casein hydrolysis were 0.05 g litre^?1 at 24 h. Peptides accumulated in rumen fluid of sheep receiving dietary ionophores. Two hours after feeding, the accumulation with monensin appeared to be of peptides of a wide M_r range, while tetronasin caused an accumulation mainly of smaller, <570 Da, peptides. Treatment of Trypticase with acetic anhydride afforded 76% protection of its peptides from degradation to ammonia in a 6-h incubation. When Trypticase was fractionated by gel filtration then acetylated, none of the fractions was protected significantly better than others.     

The effects of α-amylase inhibitors on insect storage pests: Inhibition of α-amylase in vitro and effects on development in vivo

Protein α-amylase inhibitors were prepared from wheat and their effects tested against insect storage pests both in vitro against the insect α-amylases and in vivo in insect feeding trials. Inhibitor fraction A was found to inhibit porcine pancreatic α-amylase but not insect α-amylases, whereas fractions B, C and D (0.28) did not inhibit porcine pancreatic α-amylase but were strong inhibitors of digestive α-amylases from larvae of Tribolium confusum, a storage pest of wheat products, and Callosobruchus maculatus, a storage pest of legume seeds. Fraction D, which was a single polypeptide of M_r 13 000 was the most effective inhibitor in vitro. It would appear that the degree of inhibition by the wheat α-amylase inhibitor preparations can be correlated with the presence of the M_r 13 000 (0.28) polypeptide since the purer this polypeptide the stronger was the inhibition; fraction A which contained two polypeptides of M_r 60 000 and 58 000 caused no inhibition. The effects of fractions B and C on larval development were determined in insect feeding trials. With C. maculatus both fractions were toxic, their relative effectiveness being directly paralleled by their effectiveness observed in vitro. Only fraction C was tested against T. confusum in feeding trials. Despite this fraction being equally effective against both pests in vitro it had very little effect upon larval development of T. confusum in vivo, thus suggesting that this organism is able to detoxify the wheat α-amylase inhibitors. As far as the authors are aware, this is the first time that the effects of identified inhibitor fractions have been monitored both in vitro and in vivo. The results, in contrast to previous proposals, suggest that selecting wheat varieties for high α-amylase inhibitory activity may not be a very reliable criterion in selecting for insect resistance.     

Biochemical similarity of Schizosaccharomyces pombe ras1 protein with RAS2 protein of Saccharomyces cerevisiae

Schizosaccharomyces pombe contains single ras oncogene homologue, ras1, that functions in the signal transduction pathway conducting the cell's mating processes. To understand the biochemical basis of yeast ras proteins, we have purified the ras1 protein and compared the major biochemical constants with those of RAS2 protein from Saccharomyces cerevisiae and mammalian ras proteins. The purified ras1 protein showed a remarkably high K_d value for GDP binding (178 nM) and for binding with ATP. In contrast, the K_d value for GTP binding and the rate of GTPase activity were 64 nM and 77 × 10^?6 s^?1 at 37°C, respectively; both were higher than normal p21^ras protein, but at the same level as the RAS2 protein. We directly measured rate of GTP binding and GDP binding which were 3.9 × 10^?3 s^?1 and 1.8 × 10^?3 s^?1 at 30°C, respectively. On the other hand, exchange rates between bound and free nucleotides remained almost constant throughout the tested combination of GTP and GDP, and were several-fold lower than the binding rate. These results suggest that the release of the guanine nucleotide is the rate-limiting step in the ras–GTP/GDP cycle. As a whole, the biochemical properties of the ras1 protein are close to those of the RAS2 protein, although these two proteins function differently in the signal transduction pathway in the cells.     

Immunocytochemical and biochemical studies of the mobilisation of storage oil-bodies and proteins in germinating cotyledons of oilseed rape,Brassica napus

Seeds of Brassica napus L cv Mikado contain about 25% w/w protein in addition to 40–50% w/w storage oil. About 50% of the seed protein is the legumin-like neutral protein, cruciferin, and a further 20% is the small basic protein, napin. The only other major seed protein (20% of total) is a polypeptide of apparent molecular mass (M_r) 19 000±200, which is associated with the membranes of the storage oil-bodies. The purification of this protein and preparation of monospecific antibodies have recently been reported. The kinetics of protein and oil mobilisation and the subcellular distribution of the M_r 19 000 oil-body protein have been studied by techniques including sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), gas-liquid chromatography (GLC), sucrose density gradient fractionation, and electron microscop-immunocytochemistry. The results show that the mobilisation of the storage products of rapeseed occurs in at least three distinct phases: (1) a lag phase of 10–15 h, (2) breakdown of cruciferin and napin from 12 h until day 3, (3) breakdown of storage oil and oil-body membranes from day 2 until day 7. The M_r 19000 protein was localised on oil-body membranes in early stages of germination but was later associated with a light membrane fraction, which probably contained oil-body ghosts. Relatively little difference in the kinetics of the mobilisation of storage oils and proteins was found whether seedlings were grown in the light or in the dark. The implications of these results for the mechanism of storage oil mobilisation in oilseeds are discussed.     

Expression of HIV-1 nef in yeast: The 27 kDa nef protein is myristylated and fractionates with the nucleus

The nef gene of human immunodeficiency virus type 1 (HIV-1) has been expressed in the yeast Saccharomyces cerevisiae to produce native Nef proteins. The proteins of M_r 27 kDa and 25 kDa, produced by translation from the first and second start codons of the nef gene react with human HIV-1 antisera. Under low-level steady-state expression conditions, Nef27 undergoes myristylation and is targeted to the nuclear fraction while Nef25 is not myristylated and not nuclear localized. When produced rapidly and to high levels, Nef27 is initially present in the cytoplasm as a soluble myristylated protein that later fractionates with the nucleus.     

Charakterisierung von Weizensorten durch SDS-Polyacrylamidgel-Elektrophorese (SDS-PAGE) und zweidimensionale Elektrophorese (2D-PAGE) der Glutenine

Zusammenfassung Vierundzwanzig Weizensorten wurden durch SDS-PAGE und 2D-PAGE in horizontalen, ultradünnen Gelsystemen mit Silberfärbung auf Glutenin-Untereinheiten analysiert. Das Auftreten der hochmolekularen Untereinheiten 2 (codiert auf Weizenchromosom Glu-1A) bzw. 3 und 10 (Glu-1D) sowie 5 und 9 (G1u1B) ist mit guten Backeigenschaften (A-Qualität) der Mehle korreliert. Zwischen den hochmolekularen Untereinheiten (Gruppe A, HMW-Untereinheiten,M _r = 90000–125000) und den niedermolukularen Gluteninen (Gruppe B, LMW-Untereinheiten;M _r = 43 500–56 000) tritt eine bisher wenig beachtete Gruppe mit mittleren Molekulargewichten (Gruppe AB, MMW-Untereinheiten;M _r = 56 500–80 000) auf, die ebenfalls sortenspezifische Unterschiede zeigt.In der zweidimensionalen Elektrophorese zeigt sich neben der ladungsbedingten Heterogenität der einzelnen Untereinheiten bei einigen Sorten eine weitere, anscheinend eigenständige Gruppe BC mit niederem Molekulargewicht (M _r = 40 500–43 500). Die Proteine dieser Gruppe besitzen, im Gegensatz zu den umgebenden basischen Gruppen B und C, deutlich niedrigere isoelektrische Punkte.

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Characterization of glutenins in wheat varieties by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2D-PAGE)

Summary Twenty-four wheat varieties were analysed for glutenin subunits by SDS polyacrylamide gel electrophoresis (PAGE) and two-dimensional (2D)-PAGE using horizontal ultrathin pore-gradient gels and silver staining. The following high-molecular-weight (HMW) subunits correlated well with good baking quality (Grade A varieties): 2 (coded in wheat chromosome Glu-1A), 3 and 10 (Glu-1D) and 5 and 9 (Glu-1 B). Some other grade A varieties showed the HMW subunits 2, 4, 8, and 11, which are typical for grade B and C varieties.Between the HMW subunits (group A subunits,M _r = 90000–125 000) and the low-molecular-weight (LMW) subunits (group B subunits,M _r = 43 500–56 000), the electropheretograms exhibited a group of sharp protein bands with intermediate molecular weights (MMW-subunits,M _r = 56 500–80 000). The pattern of this group, which has up to now been practically unnoticed, is also dependent on the wheat variety.In addition to the charge-dependent heterogeneity of the subunits, the 2D-electropheretograms of some varieties showed an additional protein group, denoted BC, which has a low molecular weight (M _r = 40 500–43 500). In contrast to the adjacent basic groups B and C, these BC proteins have significantly lower isoelectric points.

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Gefördert von der Arbeitsgemeinschaft Industrieller Forschungsvereinigungen (AIF) über den Forschungskreis der Ernährungsindustrie e. V.     

Major albumins of Pisum cotyledons

The albumin fraction of the cotyledons of Pisum contains two major polypeptides which together make up 34% (17% each) of the total albumin fraction. Both of these albumins (M_r～8000 and ～22000) are cotyledon specific proteins. In many Pisum lines the M_r～22000 fraction resolves into two components on Na-dodecylsulphatepolyacrylamide gels. The M_r～8000 polypeptide was broken down during germination and early seedling growth, indicating that it functions as a storage protein, while the M_r～22000 polypeptides were degraded relatively slowly. The level of both of these polypeptides was markedly reduced under sulphur deficiency conditions, the M_r～22000 components being affected to a lesser extent than the M_r～8000 component. Consistent with this, when [³⁵S]sodium sulphate was injected into the pedicel of control plants during seed development and albumins were isolated at seed maturity, polypeptides of M_r～8000 and ～22000 together accounted for a major proportion of the radioactivity in the total albumin fraction. The abundance and relatively high sulphur content of these two albumins could be significant factors in determining the nutritional value of pea seed proteins.     

Size and charge properties of the pectic and cellulolytic enzymes in a commercial enzyme preparation

Summary The size and charge properties of the pectic and cellulolytic enzymes in a commercial preparation were studied using with isoelectric focusing, nondenaturating polyacrylamide gradient gel electrophoresis, titration curve analysis and a two-dimensional technique. Enzyme activity was detected with the zymogram technique. Five major isoenzymes of endo-polygalacturonase were detected having isoelectric points (pI) of 3.2, 3.6, 3.7, 4.4, and 4.5. These separate into two major size species after PAGGE (M _r 28000 and 48000). — Endo-pectinlyase was detected at pI 3.6/M _r 38000 after two-dimensional electrophoresis. — Pectin esterase was found to have a pI of 3.5 and aM _r of 27000. — Endo-Cx-cellulases were found at pI 3.1–3.2/M _r 38000; pI 3.5/M _r 27000; pI 3.6–3.8/M _r 80000; pI 5.6/M _r 70000.

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Molekülgröße und Ladungseigenschaften von pectolytischen und cellulolytischen Enzymen in einem Handelsenzympräparat

Zusammenfassung Die Molekülgröße und Ladungseigenschaften von pectolytischen und cellulolytischen Enzymen in einem Handelspräparat wurden mittels isoelektrischer Focussierung (IEF), nichtdenaturierender Polyacrylamid-Gradienten-Gelelektrophorese (PAGGE), Titrationskurvenanalysen und zweidimensionaler Technik untersucht. Die Enzymaktivität wurde mit der Zymogramm-Technik bestimmt. Fünf Haupt-Isoenzyme der endo-Polygalakturonase (PG) wurden aufgrund ihrer isoelektrischen Punkte (pI) gefunden (PI 3,2; 3,6; 3,7; 4,4 und 4,5). Diese werden durch die PAGGE in zwei Hauptbanden mit den MolekülgrößenM _r 28000 und 48000 aufgetrennt. — Endo-Pectinlyase (PL) wurde bei pI 3,6/M _r 38 000 nach 2-D-Elektrophorese gefunden. — Für Pectinesterase (PE) wurde ein pI von 3,5 und ein Molekulargewicht von 27 000 bestimmt. — Endo-Cx-Cellulasen wurden bei pI 3,1–3,2/M _r 38 000; pI/M _r 27 000; pI 3,6–3,8/M _r 80 000; pI 5,6/70000 gefunden.

     

Sequencing of a 17·6 kb segment on the right arm of yeast chromosome VII reveals 12 ORFs,including CCT,ADE3 and TR-I genes,homologues of the yeast PMT and EF1G genes,of the human and bacterial electron-transferring flavoproteins (β-chain) and of the Escherichia coli phosphoserine phosphohydrolase,and five new ORFs

A 17·6 kb DNA fragment from the right arm of chromosome VII of Saccharomyces cerevisiae has been sequenced and analysed. The sequence contains twelve open reading frames (ORFs) longer than 100 amino acids. Three genes had already been cloned and sequenced: CCT, ADE3 and TR-I. Two ORFs are similar to other yeast genes: G7722 with the YAL023 (PMT2) and PMT1 genes, encoding two integral membrane proteins, and G7727 with the first half of the genes encoding elongation factors 1γ, TEF3 and TEF4. Two other ORFs, G7742 and G7744, are most probably yeast orthologues of the human and Paracoccus denitrificans electron-transferring flavoproteins (β chain) and of the Escherichia coli phosphoserine phosphohydrolase. The five remaining identified ORFs do not show detectable homology with other protein sequences deposited in data banks. The sequence has been deposited in the EMBL data library under Accession Number Z49133.     

A preliminary study of monosaccharide composition and α‐glucosidase inhibitory effect of polysaccharides from pumpkin (Cucurbita moschata) fruit

In this work, crude polysaccharide extracts were extracted from pumpkin (Cucurbita moschata) fruit by hot water. After removal of proteins and purification, polysaccharides of pumpkin fruit (PP1‐1) were subjected to structural identification. Gas chromatography analysis indicated that PP1‐1 comprised of galactose (86.4%), and glucose (13.6%). The molecular weight of PP1‐1 was measured to be 0.87 × 10⁴ Da by gel permeation chromatography. The inhibitory kinetic evaluation showed that it was non‐competitive inhibition of PP1‐1 on the α‐glucosidase‐catalysed hydrolysis of PNPG. The Michaelis–Menten constant (K_m) was 0.106 m , and the inhibitory constants (K_i), 0.435 mg.     

Antimutagenicity of polyphenol-rich fractions from sorghum bicolor grain

Polyphenols extracted from a bird-resistant sorghum (Sorghum bicolor (L) Moench) grain cultivar SSK30 were separated into three crude fractions: non-tannin polyphenols with small M_r (F₁); proanthocyanidins with M_r values between 2000 and 10000 (F₂); and proanthocyanidins with much larger M_r values of around 10000-50000 (F₃). Each fraction was tested for mutagenicity using mutants of Salmonella typhimurium (the Ames test) or the somatic mutation and recombination test (SMART) employing Drosophilu melanogaster. None of the fractions was positive with either test. On the other hand the crude polyphenols all acted as antimutagens when coincubated with mutants of S typhimurium and standard mutagens (sodium azide, daunomycin and 2-aminofluorene). The order of antimutagenicity was F₃> F₂> F₁, a decrease with decreasing M_r. It is possible that a different mechanism of polyphenol antimutagenicity occurs against the mutagen sodium azide when compared with the mutagens daunomycin and 2-aminofluorene.     

A new candidate protein for high lysine content in wheat grain

Lysine is the most limiting essential amino acid in cereal grains, so that grain lysine content is important for human nutrition and livestock growth. Translation elongation factor 1α (EF‐1α) from cereal embryo was recently reported to be rich in lysine, and the possibility of using this protein as a marker for feed quality was explored in maize. In this study we used immunochemical methods to investigate the relationship between the content of EF‐1α and other proteins from wheat germ and lysine content in both hexaploid (bread) wheats and diploid wheat progenitors to the wheat A‐genome. The levels of grain lysine, as well as their variation between lines or cultivars, were greater for the diploid wheats. While there was a significant correlation between the levels of EF‐1α and grain lysine content, the binding of antibodies to a protein of M_r 37 000 showed a higher correlation. This protein was characterised by amino acid sequencing as fructose 1,6‐bisphosphate aldolase. The possibility of using fructose 1,6‐bisphosphate aldolase as a marker for feed quality and development of a simple ELISA for quantification of lysine in wheat is demonstrated. © 2000 Society of Chemical Industry     

Cloning and sequence of ADP-ribosylation factor 1 (ARF1) from Schizosaccharomyces pombe

A gene encoding a homologue of the ADP-ribosylation factor (ARF) family of small GTP binding proteins was cloned from a Schizosaccharomyces pombe cDNA library by a functional screen of suppressors of sensitivity to 3-aminotriazole in a gcn3 null strain of Saccharomyces cerevisiae. Two independent isolates each contained the full coding region of the ARF1 gene. The encoded SpARF1 protein has a predicted molecular weight of 20 618 and is 88% and 79% identical to human and S. cerevisiae ARF1 proteins, respectively. As independent isolates were obtained, this effect of the SpARF1 appears to be a real phenomenon, but cannot currently be easily understood within the context of the evidence for a role(s) for ARF proteins in the protein secretory pathway.     

Characterisation of whey protein isolate–gum tragacanth electrostatic interactions in aqueous solutions

The main objectives of this study were to measure molecular parameters of gum tragacanth by GPC‐MALLS system and investigate the complexation behaviour of whey protein isolate/gum tragacanth mixed dispersions (0.5 wt% total biopolymer concentration) as a function of pH (7.00–2.00) and the biopolymer mixing ratio (r = 0.1–10) using spectrophotometric, zeta potential and precipitate yield determination methods. GPC‐MALLS revealed that gum tragacanth contains relatively heterogeneous particles with high weight‐average and number‐average (M_w = 7.74 × 10⁵ g mol^?1 and M_n = 3.87 × 10⁵ g mol^?1) molecular mass and high dispersity index (~2.04 ± 0.3). Results of complexation displayed that as the biopolymer mixing ratio increases, the net neutrality shifts to the higher pHs. The critical values associated with the complex structure formation were found at r = 2 in which the charge density of the mixture was near zero at a wide range of pH (3.0–4.0). However, the highest precipitate yield achieved in pH 3.4.     

Nutrient composition and the use of solubility to estimate rumen degradability of food proteins in cattle

The use of protein solubility to estimate protein degradability in cattle was tested using 12 by‐products representing agricultural and distillers' food raw materials (RM). Agricultural RM included cereals (rice bran, maize gluten feed), legumes (field beans, soybean hulls) and oil‐seeds (rape meal, sunflower meal). Distillers' RM involved dark grains (DG1, DG2, DG3) and malts (MT1, MT2, MT3). Soluble proteins, as proportions of total soluble N (TSN), were extracted from RM and their undegraded residues (RU) after 18 h of in sacco rumen incubation in cattle (dg₁₈) by using water (albumin), salt (globulin), acid (glutalin 1) and alkali (glutalin 2) in succession. RM and RU differed significantly for all soluble proteins (P < 0.001). While albumin was the major protein in legume RM (0.74TSN), glutalin 1 was the major protein in legume RU (0.54TSN). Cereals were the most variable group, where maize gluten contained five times more albumin and two times more TSN in RM and three times more glutalin 1 + 2 in RU than those in rice bran. Distillers' RM contained slightly less albumin (0.53 vs 0.56TSN) but over twice as much glutalin 1 (0.29 vs 0.12TSN) as agricultural RM. Albumins were the most (0.55TSN, RM; 0.16TSN, RU) and glutalin 1 the least (0.21TSN, RM; 0.48TSN, RU) degradable proteins. There were moderate to strong correlations between protein solubility, dg₁₈ and acid detergent‐insoluble N (ADIN). ADIN correlated satisfactorily with glutalin 1 + 2 (r = ?0.55, RM and ?0.70, RU), TSN (r = ?0.75, RM and RU) and slowly degradable N, (SDN; r = ?0.70, all). TSN in all RM related well with SDN (r = 0.65) and dUN (r = 0.72). TSN in distillers' RM correlated closely with SDN (r = 0.91) and dUN (r = 0.96). Glutalin 1 in distillers' foods correlated extremely well (r = 0.94, RM and 0.93, RU) with dUN. Globulins correlated most consistently with SDN (r = 0.82, all; r = 0.77, agricultural; r = 0.92, distillers' RM). It is possible to predict protein degradability from the presence or absence of soluble proteins in various foods. While ADIN may be more suitable to predict DUN, globulins showed more potential to predict SDN in various foods. However, it may be necessary to be selective in choosing solvents for various foods. Further studies must validate this method by using a greater range of foods before suggesting its routine use for food evaluation. © 2001 Society of Chemical Industry