In vitro renaturation of bovine beta-lactoglobulin A leads to a biologically active but incompletely refolded state

When bovine beta-lactoglobulin (beta-LG) was refolded after extensive denaturation in 4.8 M guanidine hydrochloride (GuHCl), the functional activity of the protein, retinol binding, as measured by the enhancement of this ligand's fluorescence, was completely recovered. In contrast, the room-temperature tryptophan phosphorescence lifetime of the refolded protein, a local measure of the residue environment, was approximately 10 ms, significantly shorter than the phosphorescence lifetime of the untreated native protein (approximately 20 ms). The lability of the freshly refolded protein, as monitored by following the time course of its unfolding when incubated in 2.5 M GuHCl through the change in fluorescence intensity at 385 nm, was also determined and found to be increased significantly relative to untreated native protein. In contrast to the long term postactivation conformational changes detected previously in Escherichia coli alkaline phosphatase (Subramaniam V, Bergenhem NCH, Gafni A, Steel DG, 1995, Biochemistry 34:1133-1136), we found no changes in either the lability or phosphorescence decays of beta-LG during a period of 24 h. Our results are in agreement with the report by Hattori et al. (1993, J Biol Chem 268:22414-22419), using conformation-specific monoclonal antibodies to recognize native-like structure, that long-term changes occur in the protein conformation, compared with the native structure, on refolding.     

Structural basis of the Tanford transition of bovine beta-lactoglobulin

The structures of the trigonal crystal form of bovine beta-lactoglobulin variant A at pH 6.2, 7.1, and 8.2 have been determined by X-ray diffraction methods at a resolution of 2.56, 2. 24, and 2.49 A, respectively. The corresponding values for R (Rfree) are 0.192 (0.240), 0.234 (0.279), and 0.232 (0.277). The C and N termini as well as two disulfide bonds are clearly defined in these models. The glutamate side chain of residue 89 is buried at pH 6.2 and becomes exposed at pH 7.1 and 8.2. This conformational change, involving the loop 85-90, provides a structural basis for a variety of pH-dependent chemical, physical, and spectroscopic phenomena, collectively known as the Tanford transition.     

Enzymatic properties of beta-D-galactoside alpha2 leads to 6 sialytransferase from bovine colostrum

The substrate specificity and kinetic properties of a pure sialyltransferase from bovine colostrum have been examined. The transferase appears to incorporate sialic acid into the sequence, NeuAcalpha2 leads to 6Galbeta1 leads to 4GlcNAc, which is commonly found in glycoproteins. It has a strict substrate specificity for CMP-NeuAc and forms only the alpha2 leads to 6 sialyl linkage with beta-D-galactosides. N-Acetyllactosamine (Galbeta1 leads to 4GlcNAc) and asialo-glycoproteins containing the N-acetyllactosaminyl linkage at the nonreducing ends of the oligosaccharides prosthetic groups are the best acceptor substrates. Isomers of N-acetyllactosamine with beta1 leads to 3 or beta1 leads to 6 glycosidic linkages are less than 1% as effective as acceptor substates as the beta1 leads to 4-linked isomer. Lactose (Galbeta1 leads to 4Glc) is also a poor acceptor, indicating the importance of the 2-acetamido group in the N-acetylglucosaminyl residues. The unnatural substrate beta-methyl-L-arabinopyrano-side, a five-carbon analog of beta-methyl-D-galactoside which contains no 6-hydroxyl, also acts as a poor acceptor of the transferase and the sialylated product has been partially characterized. Kinetic properties of the enzyme in the presence and absence of inhibitors suggest that the transferase has an equilibrium random order mechanism.     

Mismatch repair deficiency leads to a unique mode of colorectal tumorigenesis characterized by intratumoral heterogeneity

In order to determine the effects of mismatch repair (MMR) deficiencies in sporadic colorectal carcinomas, 45 such cancers were examined using a sensitive method called crypt isolation technique. Loss of heterozygosity (LOH) in the MSH2 or MLH1 gene was more frequently observed in replication error (RER) (+) carcinomas than in RER (-) carcinomas, which implied that loss of one normal allele could partly affect repair capacity. MSH2 gene defects at both alleles were observed in two carcinomas, which showed severe repair deficiencies. Interestingly, unlike the situation observed in the p53 gene, the MSH2 and MLH1 genes did not show complete LOH. Novel crypt isolation-based subpopulation (CISP) analysis demonstrated that at least two distinct carcinoma subpopulations existed in most carcinomas that showed incomplete LOH; one with and one without LOH. In one carcinoma that had germline mutation and somatic incomplete LOH of the MSH2 gene, the mutator phenotype was only observed in populations affected in both alleles. Thus, the MSH2 gene appears to possess the two hits mechanism of tumor suppressor genes. However, unlike the tumor suppressor genes, MMR gene defects lead to a unique mode of colorectal tumorigenesis characterized by intratumoral heterogeneity.     

Expression of bovine beta-lactoglobulin/human erythropoietin fusion protein in the milk of transgenic mice and rabbits

We have generated several transgenic mouse lines and rabbits expressing efficiently (up to 0.3 mg/ml in mice and up to 0.5 mg/ml in rabbits) human erythropoietin in their milk as bovine beta-lactoglobulin fusion protein. Human erythropoietin cDNA was inserted in frame into exon 5 of the bovine beta-lactoglobulin gene with a linker oligonucleotide encoding the cleavage site for bacterial IgA protease. RNA analysis performed on one lactating transgenic mouse and one transgenic rabbit revealed that the fusion gene was expressed almost exlusively in the mammary gland, although low amounts of transgene-derived RNA were detectable in salivary glands and uterus or in the kidney. The fusion protein was specifically cleaved with IgA protease. The erythropoietin part obtained upon digestion had a lower molecular mass than recombinant erythropoietin produced in Chinese hamster ovary cells. By deglycosylation analysis it was shown that the difference in size was due to a different type of glycosylation. Biological activity of the fusion protein, as determined by growth stimulation of TF-1 erythroleukemia cells, was less than 15% of that of human recombinant erythropoietin. Upon digestion of the fusion protein with IgA protease, biological activity comparable to that of the recombinant erythropoietin was recovered. Transgenic males and virgin females did not show signs of enhanced erythropoiesis, but lactating females expressing the transgene displayed transient increases in their hematocrit values.     

Extreme structural heterogeneity among the members of a maize retrotransposon family

A few families of retrotransposons characterized by the presence of long terminal repeats (LTRs) have amplified relatively recently in maize and account for >50% of the genome. Surprisingly, none of these elements have been shown to cause a single mutation. In contrast, most of the retrotransposon-induced mutations isolated in maize are caused by the insertion of elements that are present in the genome at 2-50 copies. To begin to understand what limits the amplification of this mutagenic class of LTR-retrotransposons, we are focusing on five elements previously identified among 17 mutations of the maize waxy gene. One of these elements, Stonor, has sustained a deletion of the entire gag region and part of the protease domain. Missing sequences were recovered from larger members of the Stonor family and indicate that the deletion probably occurred during retrotransposition. These large elements have an exceptionally long leader of 2 kb that includes a highly variable region of approximately 1 kb that has not been seen in previously characterized retrotransposons. This region serves to distinguish each member of the Stonor family and indicates that no single element has yet evolved that can attain the very high copy numbers characteristic of other element families in maize.     

Contribution to the treatment of acute bovine mastitis with cefquinome

The recombinant human colony-stimulating factors, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are hematopoietic cytokines that increase neutrophil number and enhance their function. In patients with HIV infection, G-CSF and GM-CSF have reversed or prevented neutropenia even during periods of full-dose myelotoxic therapy. Both colony-stimulating factors (CSFs) also have improved defects in neutrophil function in the setting of HIV infection. In non-neutropenic animal models of opportunistic bacterial or fungal infections, use of CSFs has increased survival. Future clinical applications of CSFs may include the adjunctive treatment of specific HIV-related opportunistic infections in addition to an expanding role in the treatment of HIV-associated neutropenia and defects in neutrophil function.     

Olsalazine versus mesalazine in the treatment of mild to moderate ulcerative colitis

AIM: To compare the efficacy and tolerability of olsalazine sodium with enteric-coated mesalazine in inducing endoscopic remission in patients with mild to moderate active ulcerative colitis. PATIENTS AND METHODS: Patients with mild to moderate active ulcerative colitis were randomized to receive either olsalazine sodium, 3 g/day (n = 88), or mesalazine, 3 g/day (n = 80), for up to 12 weeks. RESULTS: Of the patients treated with olsalazine sodium, 52.2% achieved endoscopic remission, compared with 48.8% of patients treated with mesalazine. This difference was not significant (P = 0.67). There was a nonsignificant trend for patients with left-sided colitis or a more severe endoscopic grade to achieve remission if they were treated with olsalazine sodium than if they were treated with mesalazine. Both treatments were comparable with respect to clinical activity index and an investigator's global assessment. Seventy patients reported one or more adverse events; adverse events were seen in 45% of olsalazine sodium-treated patients and in 36% of mesalazine-treated patients. Eleven patients treated with olsalazine sodium and nine patients treated with mesalazine withdrew from the study because of adverse events. One patient treated with olsalazine sodium compared with two treated with mesalazine stopped treatment because of diarrhoea. Serious adverse events occurred in three patients treated with olsalazine sodium and in four treated with mesalazine. CONCLUSION: Therapeutic effectiveness and tolerance to the treatment did not differ between olsalazine sodium, 3 g/day, and mesalazine, 3 g/day, in inducing endoscopic remission in patients with mild to moderate active ulcerative colitis within 12 weeks of treatment.     

Characterization by ionization mass spectrometry of lactosyl beta-lactoglobulin conjugates formed during heat treatment of milk and whey and identification of one lactose-binding site

The extent of the early stage of the Maillard-type reaction that impaired functional properties of whey proteins was evaluated by electrospray ionization mass spectrometry. Under conditions of mild heat treatment (63 degrees C for 20 s) applied to milk before whey separation at room temperature 23 degrees C), a modification of the relative molecular mass of beta-lactoglobulin (beta-LG) was observed that differed from that of the native form by 324. This specific modification of beta-LG occurred in acidified whey as well as in sweet whey and increased with the extent of the heat treatment. Incubation of purified beta-LG dissolved in milk ultrafiltration permeate or in lactose solution at 50 to 80 degrees C demonstrated the presence of a lactosyl residue that was covalently bound to beta-LG; beta-casein, used as a control, showed no mass modification. Studies of kinetics showed that a maximum of 35% of the beta-LG was lactosyl-beta-LG conjugate after heat treatment at 70 degrees C for 1 h. This study provides the first direct evidence of specific lactosylation of beta-LG during the initial stage of the Maillard reaction. One of the first lactose-binding sites was identified as a Lys47 by protease mapping and analysis by means of on-line liquid chromatography combined with mass spectrometry. In addition, collision-activated dissociation performed on the lactosylated peptide beta-LG (f 46-51) showed the rearrangement reactions occurring during the fragmentation process by electrospray. A mechanism is proposed.     

Effect of heat treatment on phase and structural transformation in SmCo5 alloy powder

Conclusions The temperature range of precipitation of the Sm₂Co₁₇ phase in a single-phase SmCo₅ powder is 600–650 °C. The formation of the Sm₂Co₁₇ phase as a result of phase separation substantially decreases the degree of texturization acquired by a powder in a magnetic field. The recrystallization temperature of SmCo₅ powder lies in the range 450–500°C.Translated from Poroshkovaya Metallurgiya, No. 7(211), pp. 70–74, July, 1980.     

The whey proteins of the milk of red deer (Cervus elaphus L.). A homologue of bovine beta-lactoglobulin

Increasing plasma free fatty acids decreased the degree of glycogen depletion, and increased the citrate concentration, in slow-red (soleus) and fast-red (deep portion of vastus lateralis) muscle during exercise (approx. 50% depletion of glycogen, as against 75% in control animals). There was no effect in fast-white muscle (superficial portion of vastus lateralis). Glycogen concentration in the liver decreased by 83% in controls, but only by 23% in animals with increased free fatty acids during exercise. The decreased glycogen depletion may be partly explained by the findings that (a) plasma-insulin concentration was two- to three-fold higher in animals with increased plasma free fatty acids and (b) the exercise-induced increase in plasma glucagon was lessened by increased free fatty acids. Blood glucose was higher in the animals with increased free fatty acids after the exercise. The rats with increased plasma free fatty acids utilized approx. 50% as much carbohydrate as did the controls during the exercise.     

Nature of changes in the microstructure and properties of fine-grained iron-copper composites under heat treatment

We examine the nature of the changes that occur in the microstructure and properties of fine-grained iron-copper composites with 30 mass % (27.3 vol. %) Cu during solid-phase heat treatment and when passing through the melting point of copper. Quantitative studies of the microstructure were made during sintering of mixtures of the highly dispersed powders of the initial metals and during heating of sintered high-density fine-grained specimens. The process of microstructure transformations during liquid-phase sintering and heating of high-density fine-grained composites above the melting point of copper was found to have three stages: recovery of the crystal structure and formation of large-angle boundaries in the Fe component, an increase in Fe grain size, and formation of solid solutions by mutual diffusion of components; penetration of the liquid phase along Fe grain boundaries with a decrease in grain size because of disintegration; and a secondary growth of Fe grains and formation of a Cu matrix structure or, more likely, a matrix structure of solid solution of Fe in Cu begins to form. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 13–20, May–June, 2000.     

A method of heat treatment using the heat of rolling

Translated from Metallurg, Vol. 39, No. 4, p. 25, April, 1995.