Two-dimensional polyacrylamide gel electrophoresis map of bull seminal plasma proteins

A two-dimensional polyacrylamide gel electrophoresis map of bull seminal plasma proteins has been established. About 250 spots were detected after silver staining and polypeptides from 24 spots have been N-terminally sequenced. Major proteins already described in bull seminal plasma, like PDC-109 and aSFP, have been located on the map; proteins not yet reported in male reproductive tracts have been evidenced; for some polypeptides showing a previously unknown N-terminal sequence, structural similarities with proteins described in other organisms have been found. A reference map of seminal plasma proteins could be useful in relating protein pattern changes to physiopathological events influencing the reproductive sphere.     

Protein analysis of Strongyloides venezuelensis by two-dimensional polyacrylamide gel electrophoresis

Infective larvae, larvae in the lung and adult-stage worms in the small intestine of Strongyloides venezuelensis were analysed for protein by two-dimensional gel electrophoresis. The infective larvae were differentiated from the other two stages of parasite with 13 stage-specific spots, whereas the larvae in the lung and the adult-stage worms were identical to each other in spot patterns except for 6 spots.     

Clinical implications of the types of cryoglobulins determined by two-dimensional polyacrylamide gel electrophoresis

BACKGROUND AND OBJECTIVE: Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is a new method which can be used to study cryoprecipitates from the sera of cryoglobulinemic patients. It led to the identification of a new type of cryoprecipitate, tentatively named II-III, characterized by polyclonal IgG associated with a mixture of polyclonal and monoclonal IgM. Some discrepancies with the conventional classification of cryoglobulins were revealed. The association of particular clinical features with the classification of cryoglobulins by 2-D PAGE is examined. DESIGN AND METHODS: Sixty consecutive patients affected by cryoglobulinemic syndrome with mixed cryoglobulins were included in the study. All patients were evaluated for cutaneous, articular, hepatic, renal and nervous involvement. The washed cryoprecipitates were typed using both techniques: immunofixation electrophoresis (IFE) and 2-D PAGE. RESULTS: Sixteen (6 cases of type II and 10 of type III by IFE) of 60 cryoprecipitates (26.6%) appeared as type II-III by 2-D PAGE analysis. Nine cases were classified differently by IFE and 2-D PAGE. Mixed cryoglobulins of type II-III were not associated with a particular clinical pattern. Examining the clinical findings in the mono group (those with monoclonal IgM alone) and the poly group (those with polyclonal IgM alone or polyclonal and monoclonal IgM) we found clearly significant differences: more severe liver involvement in the poly group, and higher cryocrit and creatinine values, lower C4 level and more severe purpura in the mono group. INTERPRETATION AND CONCLUSIONS: Our results confirm the reliability of 2-D PAGE in characterizing cryoprecipitates. This sensitive method can demonstrate a higher number of monoclonal components, undetectable by IFE. Type II-III cryoglobulins are not associated with a particular clinical pattern. The presence or absence of polyclonal IgM in mixed cryoglobulins seems to be correlated with some clinical findings.     

The interaction between Mycobacterium and the macrophage analyzed by two-dimensional polyacrylamide gel electrophoresis

The intramacrophage pathogen Mycobacterium avium resides in a vacuole which displays unusual fusion characteristics, expressed as both a failure to mature into phagolysosomes and a continued access to the early recycling pathway. In contrast, compartments containing inert IgG-opsonized latex beads mature to phagolysosomes. Techniques were developed for the isolation of these particle-containing phagosomes from macrophages to facilitate analysis of phagosomal constituents by electrophoresis and autoradiography. Metabolic labeling of macrophages followed by phagosome isolation and two-dimensional polyacrylamide gel electrophoresis revealed only minor differences in the protein profiles between the M. avium and IgG-bead phagosomes despite the marked differences in the fusigenicity of the respective vacuoles. Pulse-chase labeling experiments revealed greater differences in the accessibility of Mycobacterium avium and IgG-bead phagosomes to newly synthesized proteins. These phagosome isolation techniques were extended to analyze the protein synthesis profile of intracellular M. avium for comparison with bacteria that were metabolically labeled in broth culture. Not surprisingly, the majority of polypeptides in the bacilli were common to both growth conditions. However, despite these similarities, intracellular M. avium express several unique proteins, most notably one abundant protein with a molecular weight of 51 kDa. In addition, the bacteria manifest a restricted set of proteins expressed while in stasis shortly after infection.     

Preparative two-dimensional gel electrophoresis of membrane proteins

Electrophoretic techniques, and especially two-dimensional gel electrophoresis (2-DE), have provided an indispensable set of tools for the separation of complex protein mixtures as well as for the identification of protein-protein interactions. Nevertheless, after its introduction more than twenty years ago and even with recent technical developments, the separation of integral and peripheral membrane proteins, in amounts sufficient for microsequencing, is still a difficult task. Lipids present in the membrane as well as the low solubility of hydrophobic membrane proteins result in protein aggregation both on the sample application point and on isoelectric focusing. As a consequence many proteins do not enter the first or second dimension of 2-DE. Here we describe the modification of a protocol using a combination of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate (CHAPS), chaotropic agents (thiourea, urea), Tris base and reducing agents (1,4-dithioerythritol) to improve solubilization of integral and peripheral membrane proteins. Preparative amounts of membrane proteins (up to 2 mg) were loaded during reswelling of dry immobilized pH gradients and the resulting Coomassie staining patterns were largely superimposable with silver-stained gels obtained from identical samples (4 microg). This indicates that the recovery of proteins from the sample is not significantly compromised by the scale-up procedure. A direct application of this method for the characterization and identification of membrane proteins from cellular organelles is described in another paper in this issue (I. Fialka et al., Electrophoresis 1997, 18, 2582-2590).     

Correlation of plasma protein separation patterns obtained by two-dimensional polyacrylamide gel electrophoresis and by capillary electrophoresis

We used three different electrophoretic techniques for the analysis of human plasma proteins: (i) two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), with sodium dodecyl sulfate (SDS) used only in slab gel electrophoresis; (ii) capillary isoelectric focusing (CIEF) with no denaturants; (iii) linear polyacrylamide (LPA)-filled capillary electrophoresis with SDS (SDS-CE). With technique (i), data on isoelectric point and molecular size of plasma proteins can be obtained. Techniques (ii) and (iii) are suited to obtain quantitative information on proteins. The separation principle used in technique (ii) is closely related to that used in the first dimension of technique (i), and that used in technique (iii) related to that in the second dimension of technique (i). Therefore, we could successfully correlate protein separation patterns obtained by 2-D PAGE and those obtained by capillary electrophoresis. The advantages of correlating data obtained by various electrophoretic techniques in the course of constructing a comprehensive database on human plasma proteins are discussed.     

Diagnosis of Creutzfeldt-Jakob disease by two-dimensional gel electrophoresis of cerebrospinal fluid

BACKGROUND: The diagnosis of Creutzfeldt-Jakob disease (CJD) is based on clinical and electroencephalographic criteria which do not allow a reliable diagnosis to be made during life. METHODS: Serum and cerebrospinal fluid (CSF) samples were obtained after informed consent from relatives of suspected cases of CJD referred to the German CJD surveillance unit. CSF samples from 58 definite (neuropathologically verified), 46 probable, and 34 possible CJD cases, and from 44 patients without CJD were analysed by two-dimensional gel electrophoresis (2-DE). Two investigators blinded to clinical findings recorded the presence of two proteins, p130/131. The kappa value for the level of agreement between these investigators was calculated. Results obtained were compared with the determination of neuron-specific enolase (NSE) in CSF. NSE concentrations of more than 35 ng/mL were considered indicative of CJD. FINDINGS: p130/131 was detected in 81% of definite (47/58), 80% of probable (37/46), 68% of possible (23/34) CJD cases, and in none of the other 44 cases. NSE concentrations of more than 35 ng/mL were seen in 79% of definite (46/58), 80% of probable (37/46), 59% of possible (20/34) CJD cases, and 9% of other cases (4/43). The positive predictive value for 2-DE of CSF is 100% and the negative predictive value is 69%. The level of agreement for the detection of p130/131 by two evaluators in a subset of 141 2-DE gels was a kappa of 0.93 (95% CI 0.86-0.99). Of 13 cases initially classified as possible and later reclassified as definite, ten cases were identified correctly by the 2-DE analysis, indicating a better diagnostic accuracy of this test compared with the current clinical classification. None of nine cases classified as other by neuropathology had p130/131 in 2-DE. INTERPRETATION: 2-DE for p130/131 is a specific test for the diagnosis of CJD. These data suggest including detection of p130/131 as a criterion for the diagnosis of probable CJD in addition to the currently accepted criteria of a rapidly progressive dementia of less than 2 years duration, typical neurological signs, and periodic sharp-wave complexes in the EEG.     

Determination of Triton X-100 binding to membrane proteins by polyacrylamide gel electrophoresis

The molecular weight of proteins in protein-detergent complexes can be determined from ultracentrifugation experiments if the amount of bound detergent is known. A new sensitive method to measure the binding of the nonionic detergent Triton X-100 to proteins has been developed. For the membrane proteins studied, less than 50 mug of protein was required to achieve an accuracy of 10% in the determination of the detergent-protein weight ratio. The proteins were equilibrated with the detergent by electrophoresis into polyacrylamide gels containing radioactively labelled Triton X-100. The gels were then sliced and the amount of bound detergent calculated from the increase in radio-activity in the slices containing the protein zone. The amounts of protein were determined by amino acid analysis of identical protein zones cut from gels running parallel.     

Isolation of canine prolactin by polyacrylamide gel electrophoresis

The electrophoretic mobility of prolactin obtained from canine pituitary extract was studied with the aid of polyacrylamide disc electrophoresis. Using a preparative gel electrophoretic system the immunoreactive material was purified on a quantitative scale which was then used to develop a homologous radioimmunoassay for canine prolactin. The radioimmunoassay system was able to detect prolactin in the plasma of dogs after the administration of agents which would be expected to affect prolactin secretion.     

Mapping of Ras-related GTP-binding proteins by GTP overlay following two-dimensional gel electrophoresis

For identification of Rab, Rac, Rho, Ral, Rap, and Arf proteins on two-dimensional polyacrylamide gels, we have expressed full-length cDNAs of members of these protein families with the T7 RNA polymerase-recombinant vaccinia virus expression system. Membrane preparations from cells expressing the cDNAs were subjected to high-resolution two-dimensional polyacrylamide gel electrophoresis followed by [alpha-32P]GTP ligand blotting. We have mapped 28 small GTP-binding proteins relative to their isoelectric points and according to their molecular weights and by immunoblotting with specific antibodies. Rab and Rho proteins could be specifically identified by extraction of streptolysin O-permeabilized Madin-Darby canine kidney (MDCK) cells with Rab- and Rho-GDP dissociation inhibitor. We applied the reference mapping to analyze the GTP-binding patterns of synaptosome fractions from rat brain. The purified synaptosomes exhibited specific enrichment of Rab3a, Rab5a, Ral, and several other GTPases. This approach and the map we have produced should provide a useful aid for the analysis of the expression and localization of members of all families of small GTP-binding proteins in various cell types and subcellular fractions.     

Extraction of membrane proteins by differential solubilization for separation using two-dimensional gel electrophoresis

We describe the extraction and enrichment of membrane proteins for separation by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) after differential solubilization of an Escherichia coli cell lysate. In a simple three-step sequential solubilization protocol applicable for whole cell lysates, membrane proteins are partitioned from other cellular proteins by their insolubility in solutions conventionally used for isoelectric focusing (IEF). As the first step, Tris-base was used to solubilize many cytosolic proteins. The resultant pellet was then subjected to conventional solubilizing solutions (urea, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, dithiothreitol, Tris, carrier ampholytes). Following the completion of this step, 89% of the initial E. coli sample mass was solubilized. Finally, the membrane protein rich pellet was partially solubilized using a combination of urea, thiourea, tributyl phosphine and multiple zwitterionic surfactants. Using N-terminal sequence tagging and peptide mass fingerprinting we have identified 11 membrane proteins from this pellet. Two of these outer membrane proteins (Omp), OmpW and OmpX, have previously been known only as an open reading frame in E. coli, while OmpC, OmpT and OmpTOLC have not previously been identified on a 2-D gel. The prefractionation of an entire cell lysate into multiple fractions, based on solubility, results in simplified protein patterns following 2-D PAGE using broad-range pH 3.5-10 immobilized pH gradients (IPGs). Additional advantages of sample prefractionation are that protein identification and gel matching, for database construction, is a more manageable task, the procedure requires no specialized apparatus, and the sequential extraction is conducted in a single centrifuge tube, minimizing protein loss.     

Development of a two-dimensional gel electrophoresis database of human lysosomal proteins

Two-dimensional gel electrophoresis databases have been generated for a range of tissue cell and fluid types, from a number of species. A major difficulty in the development of such databases is the large number of proteins present in even a single cell type (> 10,000) and the low levels of many of these proteins. One approach to overcome these difficulties is to fractionate the cell into its organelles and generate individual databases for each subcellular component. This has the added advantage of assigning a cellular location to each protein identified. Here we report the development of a two-dimensional gel electrophoresis database of lysosomal proteins.     

Alzheimer brain proteins investigated by two-dimensional gel electrophoresis with immobilized pH gradients in the first dimension

Two-dimensional (2-D) gel electrophoresis with immobilized pH gradient 4-8 in the first dimension was applied in the analysis of Alzheimer's disease brain proteins. The silver-stained 2-D maps of extracts from the frontal cerebral cortex were examined. About 800 and 550 protein spots could be observed on the electrophoretograms from the total and buffer-soluble fractions, respectively. In comparing the gels, four protein spots could now be detected which had either been hitherto undetectable (one spot) or which were weaker (two spots) or stronger (one spot) in density (in the controls) [corrected].     

Agarose gel electrophoresis of cerebrospinal fluid proteins and analysis of the pherogram profiles by analog computer

A micro-method of agarose gel electrophoresis requiring 1--3 ml of cerebrospinal fluid for quantitative analysis of cerebrospinal fluid proteins is described. After concentration of CSF to about 50 microliter by ultrafiltration and refractometric determination of protein, approximately 20--40 microgram of total protein are used for electrophoresis. Photometric scanning of the electrophoretic pattern at two different wavelengths permits quantitative evaluation. The pherograms are analysed by means of a modified DU-PONT analog computer. Factors which influence quantitative electrophoresis are examined. In cerebrospinal fluid of normal children 15 protein fractions are demonstrated: 2 prealbumins, albumin, 5 alpha-, 3 beta- and 4 gamma-globulins.     

Single major polypeptide of a calicivirus: characterization by polyacrylamide gel electrophoresis and stabilization of virions by cross-linking with dimethyl suberimidate

A calicivirus, San Miguel sea lion virus serotype 4, isolate 15FT, externally labelled with 125I, was shown by gel electrophoresis to possess a single major polypeptide. The polypeptide migrated anomalously upon electrophoresis in two sodium dodecyl sulfate (SDS) systems: more slowly than bovine serum albumin in a continuous phosphate-buffered system and more rapidly than bovine serum albumin in a discontinuous system. Estimated molecular weights in the two systems were approximately 71,000 and 64,000, respectively. There was no clear evidence for a minor virion polypeptide. Treatment of purified San Miguel sea lion virions with dimethyl suberimidate, a cross-linking reagent, preserved virion integrity during long-term storage at 4 degrees C. Oligomeric species of the polypeptide were observed upon electrophoresis of products from cross-linked virions. Based upon a preferred polypeptide molecular weight estimate of 71,000 and distribution of oligomeric species, a calicivirion model with 120 monomeric protein units is proposed as an alternative to a 180-unit model.