A comparison of the major surfactant-associated proteins in different species

We examined the major surfactant-associated proteins in a number of species by using two-dimensional gel electrophoresis, protein blotting and immunostaining. All species have a 30,000 to 35,000 mol. wt protein group consisting of multiple isoforms with isoelectric points ranging from pH 4.4 to 5.6. The techniques used in this study have resolved three component subgroups within the 35 K group. A group of proteins at 60,000-65,000 mol. wt has also been consistently identified. We conclude that remarkable similarity exists among the major surfactant-associated proteins from various mammals with regard to isoelectric points, molecular weights and antigenic sites.     

The Characterization of Tubulin in CNS Membrane Fractions

Abstract— Rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), and a plasma membrane (PM) fraction enriched in synaptic membranes were isolated from rat forebrain. The proteins in these membrane fractions were analyzed by two-dimensional gel electrophoresis (2DGE) in the isoelectric range of 5.1 to 6.0 by a modification of the O'Farrell procedure. Proteins were detected by Coomassie Brilliant Blue staining of the electrophoretograms. The results of these analyses were compared with 2DGE analysis of cytosol proteins, with particular attention given to tubulin subunits and actin. The RER contained one major protein (53K 5.4) in the β-tubulin region with a molecular weight of 53,000 and an isoelectric point of 5.4. The SER contained at least two major proteins in the β-tubulin region; one with a migration identical to 53K 5.4 and other proteins with slightly higher apparent molecular weights and more acidic isoelectric points (54K, 5.4 to 5.3), identical to cytoplasmic β-tubulin. The PM fraction also contained multiple overlapping proteins (54K, 5.4 to 5.3) in the β-tubulin area and a trace amount of the 53K 5.4 protein. The proteins in the β-tubulin region were removed from the 2DGE electrophoretogram and digested by Staphylococcus aureus V8 protease, and the peptides separated on one-dimensional polyacrylamide gels. The peptide patterns of 53K 5.4 protein from RER and SER were almost identical and differed significantly from the cytoplasmic β-tubulin pattern; however, the peptide maps of the PM and SER β-tubulin region were identical to the cytoplasmic β-tubulin. The 2DGE analysis of RER did not contain proteins in the region of cytoplasmic α-tubulin. SER and PM contained proteins in the α-tubulin region with a similar, but not identical, peptide analysis to cytoplasmic α-tubulin. Significant amounts of actin were detected in 2DGE analysis of SER and PM, and the peptide analysis of the actin was identical to the cytoplasmic actin analysis. The RER fraction contained only trace amounts of actin. The cytosol and all membrane fractions contained a protein (68K 5.6) found among microtubule-associated proteins, as judged by molecular weight and isoelectric point. Several proteins present in all membrane fractions (61K 5.1 and 58K 5.1) bound to concanavalin A agarose.     

Separation of the cytolytic and mosquitocidal proteins of Bacillus thuringiensis subsp. israelensis

The cytolytic and mosquitocidal proteins of Bacillus thuringiensis subsp. israelensis were isolated from parasporal crystals and subsequently separated from each other. The proteins were separated by gel filtration chromatography and their molecular weights were estimated by both gel filtration chromatography and SDS-polyacrylamide gel electrophoresis. The apparent molecular weights of the mosquitocidal protein and the cytolytic protein were estimated to be 65,000 daltons and 28,000 daltons, respectively.     

The plasma proteins of Labeo umbratus (Smith) and Labeo capensis (Smith)

The plasma proteins of L. umbratus and L. capensis have been investigated by means of cellulose-acetate and polyacrylamide gel electrophoresis. Characteristic patterns were obtained for each specie although variations occur within a certain basic framework. Certain fractions were further isolated and approximate average molecular weights were found to vary between 55 000 and above 120 000 and isoelectric points between 5.78 and 4.2. Certain fractions were found to exist in dimeric form. It is concluded that the application of the human nomenclature to fish plasma protein fractions is of dubious value and that the fish fractions can only be classified after thorough biochemical investigation.     

The purification and characterization of multiple forms of mouse submaxillary gland renin

Five forms of renin, A₀, A, C, D and E, from mouse submaxillary gland were purified by a two-step procedure including chromatography on the immunoaffinity column and CM-cellulose column. Four renin fractions, A₀, A, C and E were purified to homogeneity by the criteria of polyacrylamide gel electrophoresis, analytical isoelectric focusing and Ouchterlony double immunodiffusion. All these forms of renin have molecular weights of 40 000 as determined by gel filtration on Sephadex G-100 column. No high molecular weight renin could be demonstrated. Individual renin fractions showed similar angiotensin I formation activity, 52–158 ng angiotensin I/ng protein per h. No other protease activity could be detected with hemoglobin or casein as substrate. These purified proteins showed a discrete pattern of migration under polyacrylamide gel electrophoresis. Under denaturing condition in SDS-gel electrophoresis, all but fraction D showed a protein band with a molecular weight of 30 000. Fraction D showed a major component with molecular weight of 33 000. The isoelectric points of these renin forms varied from 5.46 to 5.76. They all reacted with antibody raised against renin A and showed similar pressor response activity with 20 ng quantities of the purified proteins. The closely related characteristics of these five forms of renin were further demonstrated by their similarity in peptide mapping patterns after limited digestion with Staphylococcus aureus V8 protease. The data suggest that these proteins are homologous proteins.     

Investigations on the outer membrane proteins of Salmonella typhimurium.

The number, nature and organization of the outer membrane proteins of Salmonella typhimurium have not yet been resolved. Therefore these proteins were isolated using a concentrated solution of guanidine hydrochloride and studied using different analytical techniques. Upon chromatography on Sephadex G-200 four fractions were obtained. Only the fraction containing a protein of molecular weight 13,000 produced immunoprecipitation reactions with the antisera raised against the whole bacteria. On polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, 7 major proteins were found, with molecular weights between 13,000 and 43,000. Isoelectric focusing on 4.6% polyacrylamide gels resolved the outer membrane proteins into 10 bands with apparent isoelectric points between 5.0 and 8.4. Finally these proteins could be further resolved into as many as 50 spots where a two-dimensional electrophoresis was carried out with isoelectric focusing in the first dimension, and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate in the second dimension. These results demonstrated that the outer membrane proteins of S. typhimurium are extremely heterogeneous. To investigate the mode of organization of lipopolysaccharides in the outer membrane, the membrane proteins were separated by the liquid isoelectric focusing technique. Lipopolysaccharides were primarily found to be associated with a protein of isoelectric point 7.8.     

Isolation and partial characterization of a alpha 2-beta 1-glycoprotein from horse plasma

A alpha 2-beta 1-glycoprotein was isolated from horse plasma by classical methods. The final product appeared homogeneous by agarose gel and pore limit SDS polyacrylamide gel electrophoresis, immunoelectrophoresis and crossed immunoelectrophoresis. The protein moved in agarose gel electrophoresis just above the beta 1 region and seemed composed of a single polypeptide chain. A highly heterogenic banding pattern, focused between pH 5.1 and 6.5 was revealed by isoelectric focusing. The molecular weights determined by gel filtration on Sephadex G100 and by a pore limit polyacrylamide gel electrophoresis in presence of SDS were 65,000 and 82,300 dalton, respectively. No serological relation was found between the horse alpha 2-beta 1-glycoprotein and human and bovine plasma proteins.     

Studies on Stigma Pellicle Glycoproteins of Raphanus sativus L.

Stigma surface diffusates of Raphanus sativus were subjected to polyacrylamide gel electrophoresis. There appeared protein bands, one of which gave positive PAS reaction, indicating it was glycoprotein. SDS polyacrylamide gel electrophoresis showed that the stigma diffusates contained many protein bands. By comparing their mobilities with those of standard proteins of known molecular weights, the molecular weights of some of the major fractions were estimated to be 15000, 30000—46000 and 70000 daltons. After Schiff reagent staining two main glycoprotein fractions appeared on the SDS gel electrophoretic pattern. Their molecular weights were estimated to be lower than 15000 and higher than 100000 daltons. By using acrylamide gel isoelectric focusing method, it was found that the stigma surface diffusates contained an acidic glycoprotein with pH of about 3.7. The amino acid composition of the purified stigma glycoprotein was determined with amino acid analyzer. Glycine, glutamic acid, serine, aspartic acid were some of the predominant amino acids. The diffusates were analysed by gasliquid chromatography for sugars. Results showed that the carbohydrate fraction of the glycoprotein consisted of arabinose 17.3%; galactose 19.1%, xylose 8.1%, mannose 5.4%, glucose 23.7%, rhamnose and/or fucose 26.4%. In the stigma surface diffusates of Raphanus sativus, the content of protein was estimated to be 16% and that carbohydrate was 11%.     

Isolation of a protein from the parasporal crystal of Bacillus thuringiensis var,kurstaki toxic to the mosquito larva,Aedes taeniorhynchus

The parasporal crystal produced by a strain of Bacillus thuringiensis var. kurstaki (HD-1) contains two serologically distinct proteins. These proteins were isolated from a preparation of the parasporal crystal by Sephacryl S-300 column chromatography. Their molecular weights were estimated as 135,000 and 65,000. Both proteins were toxic to the cabbage looper, Trichoplusia ni, but only the 65,000-dalton protein was toxic to larvae of the mosquito, Aedes taeniorhynchus. Biochemical comparisons based on isoelectric focusing and peptide mapping by two-dimensional gel electrophoresis indicated that the two toxins were distinctly different.     

Characterization of B- and C-type low molecular weight glutenin subunits by electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry

Low molecular weight glutenin subunits (LMW-GS) are typically subdivided into three groups, according to their molecular weights and isoelectric points, namely the B-, C-, and D groups. Enriched B- and C-type LMW-GS fractions extracted from the bread wheat cultivar Chinese Spring were characterized using high performance liquid chromatography (HPLC) directly interfaced with electrospray ionization mass spectrometry and HPLC coupled off-line with matrix-assisted laser desorption/ionization mass spectrometry, in order to ascertain the number and relative molecular masses of the components present in each fraction and determine the number of cysteine residues. About 70 components were detected in each of the fractions examined by the combined use of these two techniques, with 18 components common to both fractions. Analysis of the fractions after alkylation with 4-vinylpyridine allowed determination of the number of the cysteines present in about 40 subunits. The proteins detected were tentatively classified based on the relative molecular masses and number of cysteine residues. Cross-contamination was found in both B- and C- fractions, along with the presence of D-type LMW-GS. The two fractions also contained unexpected components, probably lipid transfer proteins and omega-gliadins. The presence of extensive microheterogeneity was suggested by the detection of several co-eluting proteins with minor differences in their molecular masses.     

Deficiencies of Chromatophore Proteins in Some Mutants of Rhodopseudomonas spheroides with Altered Carotenoids

Chromatophore proteins of a wild type and three mutant strains of Rhodopseudomonas spheroides were examined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The mutants consisted of a green and a blue-green one, whose phenotypes were essentially the same as those of known mutants, and a brown one, which may be a double mutant and represents a new phenotype. Wild-type chromatophores contained at least six major and seven minor protein bands, with molecular weights ranging from 10,000 to 65,000. The green mutant contained the same protein bands in the same relative quantities. The brown mutant had one protein completely missing and no other alterations. The blue-green mutant was deficient in a different protein, and had reduced quantities of all proteins with molecular weights less than 25,000. Chromatophores were separated into a fraction containing the reaction centers and a fraction containing the light-harvesting bacteriochlorophyll by treatment with sodium dodecyl sulfate. Eight of the proteins were found only in the reaction center fraction, one was only in the light-harvesting fraction, and the remainder were present in both fractions. The protein missing from the brown mutant was found to be a component of the reaction center fraction, whereas the proteins which were missing from the blue-green mutant were all components of the light-harvesting fraction. Some implications for the structure and biogenesis of chromatophores are discussed.     

Vimentin and 70K Neurofilament Protein Co-exist in Embryonic Neurones from Spinal Ganglia

Abstract: The mesenchymal intermediate filament protein vimentin and the 70K component of neurofilament were detected by two-dimensional gel electrophoresis in cultures of pure sensory and sympathetic neurones derived from chick embryos. The identities of these neuronal intermediate filament proteins were confirmed by comparison of their molecular weights, isoelectric points, and peptide patterns from limited papain digestions with those of the corresponding proteins from fibroblasts and brain, respectively. A specific antibody to vimentin stained filamenteous structures and colcemid-induced coils in both neurones and associated satellite cells. In contrast, a specific antibody to the 70K neurofilament protein stained these structures solely in neurones. This neurone-specific staining, as well as its molecular weight and isoelectric point, distinguishes the 70K neurofilament protein from the 68K neurofilament as sociated protein described by others, which has been claimed to resemble the tubulin assembly protein.     

Detection of Macromolecular Fractions in HCN Polymers Using Electrophoretic and Ultrafiltration Techniques

Elucidating the origin of life involves synthetic as well as analytical challenges. Herein, for the first time, we describe the use of gel electrophoresis and ultrafiltration to fractionate HCN polymers. Since the first prebiotic synthesis of adenine by Oró, HCN polymers have gained much interest in studies on the origins of life due to the identification of biomonomers and related compounds within them. Here, we demonstrate that macromolecular fractions with electrophoretic mobility can also be detected within HCN polymers. The migration of polymers under the influence of an electric field depends not only on their sizes (one‐dimensional electrophoresis) but also their different isoelectric points (two‐dimensional electrophoresis, 2‐DE). The same behaviour was observed for several macromolecular fractions detected in HCN polymers. Macromolecular fractions with apparent molecular weights as high as 250 kDa were detected by tricine‐SDS gel electrophoresis. Cationic macromolecular fractions with apparent molecular weights as high as 140 kDa were also detected by 2‐DE. The HCN polymers synthesized were fractionated by ultrafiltration. As a result, the molecular weight distributions of the macromolecular fractions detected in the HCN polymers directly depended on the synthetic conditions used to produce these polymers. The implications of these results for prebiotic chemistry will be discussed.     

Further characterization of the beta-glycoprotein of the rabbit uterus

beta-Glycoprotein was isolated from preimplantation uterine secretions of the rabbit by gel- and ion-exchange chromatography. Two fractions, called DF1 and DF2, were analyzed by isoelectric focusing (IEF) and sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in combination with Western blotting and immunoelectrophoresis. DF1 displayed 21 bands with isoelectric points of pH 5.2-7.6, and DF2 15 bands of pH 4.2-5.7. SDS-PAGE yielded up to 14 bands with major components at molecular weights of 63,000 and 135,000 respectively. Two-dimensional gel electrophoresis of DF2 in combination with Western blotting revealed five groups of proteins of equal molecular weights but with different isoelectric points, indicating immunological identities. Glycosidase activities in uterine secretions before and after implantation were studied and compared with those of the blastocyst fluids. alpha-L-Fucosidase co-eluted with DF1, and beta-N-acetylglycosaminidase was distributed in DF1 and DF2. Both enzymes were localized on isoelectric focusing gels, and N-acetylglucosaminidase was also demonstrated in an immunoprecipitate of DF1.     

Characterization of Postmortem Human Brain Proteins by Two-Dimensional Gel Electrophoresis

Abstract: The proteins of membrane and cytosol fractions from frozen human postmortem brain were analyzed by two-dimensional gel electrophoresis (isoelectric range: 5.1–6.0) and both Coomassie-blue and ammoniacal silver staining. Cytosol preparations were analyzed from six different postmortem brains from patients with various neurologic diagnoses and immediate causes of death. Intervals between death and brain freezing (−70^oC) ranged from 2 to 20 h. The vast majority of proteins detected in these cytosol fractions had identical molecular weights and isoelectric points in each of six human brains examined. However, in some tissue samples tubulin was either quantitatively decreased or undetectable. The possibility that this partial or complete depletion of tubulin was related to postmortem interval and/or brain freezing was studied using rat forebrain tissue. Rat brain incubated at room temperature for up to 24 h did not reproduce the changes seen in the region of human cytosol tubulin. However, other changes seen in the two-dimensional electrophoretic pattern of rat cytosol proteins did relate to postmortem interval, brain freezing, or both. Rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum were prepared from three human brains, with highly reproducible two-dimensional patterns. Protein analysis of these membrane fractions revealed that human RER contained significant amounts of tubulin, in contrast to rat RER which contained no detectable tubulin. This discrepancy was elucidated by allowing rat brains to remain at room temperature for 24 h before freezing; gels of rat RER prepared from this tissue showed that tubulin subunits were present.     

Two Acidic Proteins Associated with Brain Development in Chick Embryo

The developmental changes in protein composition of the chick optic tectum were analyzed by two-dimensional gel electrophoresis. Staining with Coomassie Brilliant Blue R revealed 54 major proteins, eight of which remarkably changed their abundance during development: Four of these proteins (S8, S14, S30, and S54) increased and two of them (S7 and S37) decreased in the course of the brain development. The other two proteins (S5 and S6) appeared at specific embryonic stages and were not detected in the adult. The abundance of S5 protein was highest at day 7, and that of S6 protein at days 9-18. The two proteins were present in other regions of the embryonic brain but were not detected in the embryonic liver. The proteins were purified from the soluble fraction of embryonic chick brains by pH 5.5 precipitation, DEAE-Sepharose column chromatography, ammonium sulfate precipitation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weights of S5 and S6 proteins were 95,000 and 100,000, respectively, and their isoelectric points were about 4.5. They were compared by peptide mapping using V8 protease and found to share 11 common peptides out of 17 distinct ones. This indicates a strong degree of structural homology between these two proteins.     

Two-dimensional electrophoretic analysis of secretory-granule,granule-membrane,and plasma-membrane proteins of rat parotid cells

Secretory granules and plasma membranes were isolated from rat parotid cells and characterized enzymatically and by electron microscopy. The proteins of the secretory granule membranes, the secretory granules and the plasma membranes were characterized by two-dimensional polyacrylamide gel electrophoresis and visualized by silver staining. The granule membrane contains 166 polypeptides of which only 26 are also present in the granule contents. The membrane proteins have isoelectric points between 4.75 and 6.45 and apparent molecular weights of 17 000 to 190 000 Daltons. The granule content proteins are surprisingly complex and contain 122 polypeptides with molecular weights of 11 000 to 138 000 and isoelectric points of 4.8 to 6.55. Thirteen of these peptides are present as major species. The plasma membrane contains 172 polypeptide species with molecular weights from 17 000 to 200 000 Daltons and isoelectric points of 5.0 to 6.8. Thirty-five of the plasma membrane proteins are also present in the secretory granule membranes indicating that the two membranes have some enzymatic or structural properties in common. Thus, secretory granule membranes and plasma membranes from parotid cells have a more complex polypeptide composition than has previously been shown for membranes of this type. The systems developed are suitable for the analysis of regulatory events such as protein phosphorylation, proteolytic processing, and other types of post-translational modifications that may be important to the secretory mechanism.     

Identification of a protein component of the Ca2+-dependent K+ channel by affinity labelling with apamin

The red blood cell membrane proteins and plasma proteins of normal and spontaneously hypertensive rats were studied by uni- and bidimensional polyacrylamide gel electrophoresis. The amount of band 3, the major intrinsic protein of the erythrocyte membrane, was observed to be significantly reduced in spontaneously hypertensive rats. Plasma from these rats contained two additional heat stable proteins, characterized by a molecular weight of 16,000 daltons and isoelectric points of 4.7 and 5.1, respectively. These proteins were not detected in normotensive control Wistar Kyoto rats, in normal Wistar rats, or in Wistar rats with experimentally induced hypertension.     

植物叶片蛋白质双向电泳技术的改进与优化

通过对传统的双向电泳方法进行改进与优化,得到了一种适合于分析植物叶片蛋白质的双向电泳新方法。用改进后的方法对水稻不同时期成熟叶片蛋白质进行双向电泳分离,结果显示其稳定性和重复性好,分辨率较高,经考马斯亮蓝染色后可分辨出３００多个蛋白质（肽）点。它们的等电点和分子量主要分布于ｐ＊４．１－８．２和１０－１００ｋＤａ之间,本还就实验过程中出现的一些技术问题进行了讨论。     

Purification and characterization of a lectin from the beetle, Allomyrina dichotoma

A lectin was purified from the hemolymph of Allomyrina dichotoma larvae by affinity chromatography on acid-treated Sepharose 4B. The purified lectin showed two protein bands on polyacrylamide gel electrophoresis. These two lectin bands (allo A-I and -II) were separated by DEAE-Cellulofine column chromatography. By gel filtration on Sephadex G-100, the molecular weights of allo A-I and -II were estimated to be 65,000 and 66,500, respectively. On the other hand, by SDS-polyacrylamide gel electrophoresis after cross-linking of subunits with glutaraldehyde, they are estimated to be 38,000 and 39,000, respectively. On SDS-polyacrylamide gel electrophoresis, it was proved that both allo A-I and -II lectin consisted of two subunits, respectively. The molecular weights were 17,500 and 20,000 for allo A-I, and 19,000 and 20,000 for allo A-II. The isoelectric points of allo A-I and -II were estimated to be 6.4 and 5.9, respectively. On double immunodiffusion, allo A-I and -II gave single precipitin lines, which fused completely with each other, against the antibody to crude allo A. The hemagglutinating activity of allo A-I and -II was inhibited only by beta-linked D-galactose such as lactose and lactulose.