Four gel systems for electrophoretic fractionation of membrane proteins using ionic detergents

Membrane proteins were fractionated electrophoretically in polyacrylamide gels containing either anionic or cationic detergent at either pH 2.4 or 8.3. In all four systems, polypeptides migrated as monomers bearing the charge of the detergent ion and semi-logarithmic molecular weight–mobility relationships pertained. Electrophoresis of erythrocyte membrane proteins in these systems yielded very similar protein staining patterns but revealed significant differences in sialoglycoprotein migration.     

Rhythmic chloroplast migration in the green alga Ulva: dissection of movement mechanism by differential inhibitor effects

Rhodopseudomonas viridis thylakoid membrane polypeptides were characterised by SDS gels, 2 D gels and surface-specific iodination. Four polypeptides with apparent molecular weights of 38 000, 33 000, 27 000, and 24 000 (reaction centre) and three low molecular weight polypeptides 11 000, 8000 and 6000 (probably light harvesting polypeptides) were identified. Antibodies were produced against the polypeptides eluted from SDS gels and tested for specificity by an immunoblotting assay. The antibodies were bound to the membranes and viewed by electron microscopy using a modification of the ferritin labelling technique. It is suggested that antigenic determinants for the 38 000, 33 000, and 27 000 reaction centre polypeptides and the 11 000 and 8000 low molecular weight polypeptides are present on the cytoplasmic membrane surface. The 33 000, 27 000, 11 000 and 6000 polypeptides appear to have surface-located residues which can be iodinated. The photosynthetic membrane of Rps. viridis appears to be a highly asymmetrical membrane.     

Redetermination of the molecular weights of the components of the pyruvate dehydrogenase complex from E. coli Kl2+.

The validity of molecular weight determination in SDS-polyacrylamide gels for the three components of the pyruvate dehydrogenase complex: pyruvate dehydrogenase, dihydrolipoamide transacetylase, and dihydrolipoamide dehydrogenase has been checked by measuring their free electrophoretic mobilities and their retardation coefficients. A linear relationship between these parameters has been found for all three enzymes as compared with standard proteins. This substantiates earlier molecular weight determinations in SDS-polyacrylamide gels for the components of the pyruvate dehydrogenase complex which are confirmed by this study for different acrylamide gel concentrations.     

The Immunological Identification of Brain Proteins on Cellulose Nitrate in Human Demyelinating Disease

Abstract: An immunological technique has been employed to identify proteins, separated in polyacrylamide gels, which show changes in brain samples from cases of multiple sclerosis and subacute sclerosing panencephalitis. Sodium dodecylsulphate-treated proteins in particulate and soluble fractions were separated in polyacrylamide slab gels, transferred electrophoretically onto cellulose nitrate sheets, incubated with specific antisera and visualized by an immunoperoxidase method. Protein bands showing changes were identified using antisera raised against the myelin basic and Wolfgram proteins, the neurofilament triplet proteins, tubulin and glial fibrillary acidic protein. In addition to the loss of myelin proteins, decreases in the neurofilament proteins and in tubulin were seen in both multiple sclerosis and subacute sclerosing panencephalitis samples. The distribution of glial fibrillary acidic protein polypeptides in the particulate and soluble fractions of plaque samples appeared to vary according to the degree of fibrosis. Changes in the levels of the myelin-associated glycoprotein, the lower molecular weight component of the Wolfgram protein, albumin and immunoglobulin G, none of which were visualized by protein staining, were also seen. This immunological technique has allowed a closer examination of changes occurring in brain protein spectra in multiple sclerosis and subacute sclerosing panencephalitis.     

The polymorphism and structural homology of storage polypeptides (hordein) coded by the Hor-2 locus in barley (Hordeum vulgare L.)

Two-dimensional mapping (isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) of the polypeptide components of “B” hordein fractions from eight barley varieties of widely different ancestry has been carried out. The relative positions of 47 different polypeptides were mapped, there being between 8 and 16 present in any one variety. The individual polypeptides differed in their distribution patterns; some were present in a number of varieties, while others were restricted to one or two. They also differed in their relative contributions to the total hordein fraction, both within and between varieties. The structural homology of the major polypeptides was compared by cleavage at methionine residues with cyanogen bromide and separation of the peptides on gradient gels. The polypeptides were classified into three groups which gave cleavage patterns with either two (class I), four (class II), or five (class III) low molecular weight bands. Class III polypeptides were found in all eight varieties, but in seven of the varieties class I or class II polypeptides were also present. With one exception, polypeptides migrating in the same position in different varieties gave identical or almost identical patterns. The three classes of polypeptides showed different distributions on the two-dimensional gels. Classes II and III polypeptides had a similar range of isoelectric points (pH 6.5–8.0), but all of the class II polypeptides were of slightly lower molecular weight. Class I polypeptides had a wider range of pI and molecular weight; the most alkaline and the lowest molecular weight polypeptides were in this group. The hordein fractions from a number of other barley varieties were compared with that of Julia. All had major polypeptides which migrated with ones present in Julia, but they differed in the relative amounts of these and in the absence of some polypeptides and the presence of others. B hordein is coded for by a single locus which has been suggested to be a complex multigenic family derived by duplication and divergence of a single gene. The data reported here provide support for this hypothesis and suggest that both mutations in the duplicated genes and recombination within the locus may have contributed to the polymorphism of the polypeptides.     

Characterization of a seventh different subunit of beef heart cytochrome c oxidase. Similarities between the beef heart enzyme and that from other species.

Beef heart cytochrome c oxidase has been resolved into seven subunits by electrophoresis in highly cross-linked gels containing urea and sodium dodecyl sulfate. The molecular weights of the polypeptides are estimated to be I, 35 400; II, 24 100; III, 21 000; IV, 16 800; V, 12 400; VI, 8200; and VII, 4400. It has been shown that subunits II and III can coelectrophorese on standard sodium dodecyl sulfate-polyacrylamide gels and appear as a single component with an apparent molecular weight of 22 500. This accounts for previous reports that the beef heart enzyme contains only six subunits. Amino acid analysis of the isolated subunits I, II, and III revealed that they have polarities of 35.5, 44.7, and 39.9%, respectively. All three subunits have an extremely high leucine content and a low percentage of basic amino acids relative to subunits IV-VII. The size, number, and properties of subunits in the beef heart cytochrome c oxidase complex suggest that it has essentially the same subunit structure as the complexes isolated from Saccharomyces cerevisiae and Neurospora crassa.     

Structural characterization of developmentally expressed antigenic markers on chicken erythrocytes using monoclonal antibodies

Monoclonal antibodies selected for embryonic and adult erythrocyte specificity have been used to characterize developmentally expressed markers on the surfaces of mature circulating erythrocytes of young and adult chickens. The data presented demonstrate that the antigenic changes which occur on the avian erythrocyte membrane with organismic maturation can be accounted for, at least in part, by changes in the expression of structurally different, but possibly related polypeptides. Monoclonal antibodies selected for specific reactivity with the erythrocytes of newly hatched chicks recognize a glycoprotein of 48,000 daltons apparent molecular weight. On two-dimensional isoelectric focusing gels, this antigen, which appears identical in all strains studied, displays microheterogeneity; consisting of eight to nine closely spaced spots with an isoelectric midpoint of approximately 5.5. This antigen is not expressed on the circulating erythrocytes of mature birds; however, an antigen with similar, but perhaps not completely identical structure, can be detected within the adult bone marrow. The monoclonal antibodies which show preferential binding to the circulating erythrocytes of adult birds also immune precipitate an antigen of 48,000 daltons apparent molecular weight, but this antigen has a more basic isoelectric point. The adult antigen is polymorphic. Slightly different patterns were obtained on two-dimensional gels with erythrocytes from inbred birds having different major histocompatibility genotypes. It has a major component near pH 7.0 and additional focusing spots usually occurring at a slightly lower molecular weight near pH 6.8 or 6.6 depending upon strain. Competitive radiobinding assays with B-system-specific alloantisers suggest that these antigens may in fact be antigens of the polymorphic BG locus of the chicken major histocompatibility complex. One-dimensional peptide mapping of the immune precipitated embryonic and adult erythrocyte polypeptides demonstrate that the antigens are borne on distinct but possibly related polypeptides. Both common and unique peptide fragments are found in the digestion products. Selective solubilization of the chicken erythrocyte membrane suggests that the antigens are integral membrane proteins extractable with nonionic detergent but not with reagents which remove peripheral proteins.     

Characterization of the DNA-cellulose-binding proteins from Escherichia coli K 12

The various [35S]DNA-binding proteins present in lysates of Escherichia coli K 12 cells have been analyzed by means of two-dimensional SDS-polyacrylamide gel electrophoresis. The proteins were isolated by the DNA-cellulose technique and eluted by increasing concentrations of NaCl (0.15, 0.4, 0.6 and 2 M). Only 2% of the total 35S radioactivity in the lysate became bound to the DNA-cellulose column. A total of 237 polypeptides were detected and the distribution among the salt eluates were 85, 83, 40 and 29 polypeptides, respectively. The 40 major polypeptides with regard to concentrations were also identified from gels stained with a protein-specific reagent. The polypeptides could be divided into two main groups according to pI values, namely, acidic polypeptides (total number, 174) and basic polypeptides (total number, 63). The ratio between acidic and basic polypeptides decreased with increasing salt concentrations in the eluates. The majority of the basic polypeptides had molecular weights in the range 10 000-30 000, whereas the acidic polypeptides had molecular weights from 10 000 to 165 000.     

Isoelectric points and molecular weights of salt-extractable ribosomal proteins.

Rat liver ribosomes prepared in low salt buffer contain basic and acidic proteins not found on ribosomes washed in high salt buffer. Proteins extracted from liver ribosomes by 500 mM KCL were characterized by acid urea-polyacrylamide gel electrophoresis, sodium dodecyl sulfate - polyacrylamide gel electrophoresis and gel isoelectric focusing. The salt-solubilized proteins contain 12 polypeptides with a molecular weight over 67000, several polypeptides with molecular weights less than 67 000, and three polypeptides whose molecular weight exceeded 130 000. Ten to 12 of the proteins were basic, and about 24 acidic proteins were partially or wholly extracted from the ribosomes. Four of the acidic proteins have isoelectric points less than 4.5.     

Polypeptide composition of purified QH2:cytochrome c oxidoreductase from beef-heart mitochondria

1. The polypeptide composition of purified QH2: cytochrome c oxidoreductase prepared by three different methods from beef-heart mitochondria has been determined. Polyacrylamide gel electrophoresis in the presence of dodecyl sulphate resolves eight intrinsic polypeptide bands; when, in addition, 8 M urea is present and a more highly cross-linked gel is used, the smallest polypeptide band is resolved into three different bands. 2. The identity of several polypeptide bands has been established by fractionation. The two heaviest polypeptides (bands 1 and 2) represent the so-called core proteins, band 3 the hemoprotein of cytochrome b, band 4 the hemoprotein of cytochrome c1, band 5 and Rieske Fe-S protein, band 6 a polypeptide associated with cytochrome c1 and identified with the so-called oxidation factor, and band 7 a polypeptide peptide associated with cytochrome b. 3. The validity of molecular weight estimate for the polypeptides of the enzyme based on their mobility on dodecyl sulphate gels has been examined. The polypeptides of bands 1, 2 and 3 showed anomalous migration rates. The molecular weights of the other polypeptides have been estimated from their relative mobilities on either dodecyl sulphate gels or 8 M urea-dodecyl sulphate gels as 29 000, 24 000, 12 000, 8000, 6000, 5000 and 4000, respectively. 4. The stoicheiometry of the different polypeptides in the intact complex was determined using separate staining factors for the individual polypeptide band.     

Localization of zein genes in maize

The band patterns of zein polypeptides were determined for many commercial inbred corn lines and maize stocks using isofocusing in agarose gels and sodium dodecyl sulfate (SDS)-urea gels. Each inbred line or homozygous maize strain genotype has a distinct zein profile which has been catalogued according to the distance of charge migration and molecular weight (kilodaltons). Several zein polypeptides were mapped to chromosomes 4 and 10 with the use of reciprocal translocations. The mapping of at least two polypeptides on distal 4L and 10L had not been previously reported. The general methods used in the present research will permit the mapping of all the zein polypeptides to chromosomal sites.Pioneer Hi-Bred International provided financial support.     

Evaluation of cross-linked polypeptides in SDS gel electrophoresis

The behavior of covalently cross-linked protein oligomers in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate has been compared with that of reduced polypeptides of known molecular weight. Over a limited range of molecular weights the two groups of proteins behave similarly with marked differences in mobility apparent only above 150,000 daltons. However, at all molecular weights there is a tendency for the cross-linked proteins to migrate faster than standard proteins; this could lead to overestimation of apparent molecular weights by 5–15% when the oligomers are used as ealibrating standards.     

Isolation of separate mRNAs for α- and β-Tubulin and characterization of the corresponding in vitro translation products

The messenger RNAs coding for α- and β-tubulin have been isolated from embryonic chick brain. Although the mRNAs for the two tubulin subunits have been resolved on native gels, they are very similar in molecular weight (650,000 daltons) as judged by mobility on denaturing gels containing methyl mercury. The mRNAs for β- and γ-actin have also been resolved on native gels, but migrate as an unresolved peak (molecular weight 650,000–700,000 daltons) under denaturing conditions. Since the nonmuscle actins are substantially smaller proteins than α- and β-tubulin, the large size of chick nonmuscle actin mRNAs suggests an unusually long untranslated region.Since tubulin and actin polypeptides are internal structural proteins, one would expect them to be synthesized only on free polysomes. Translation of mRNA derived directly from a purified membrane fraction or by puromycin release from that fraction, however, showed the synthesis of a small proportion of these proteins on polysomes that are membrane-associated. Peptide mapping has in all cases confirmed the identity of the products of cell-free synthesis with authentic α-tubulin, β-tubulin and actin. Approximately 67% of the α- and 13% of the β-tubulin chains produced by in vitro translation are competent for co-assembly into microtubules with added carrier microtubule protein.     

Study of human erythrocyte membrane proteins by 2-dimensional electrophoresis

Fractionation of human erythrocyte membrane proteins was performed using a modification of two-dimensional gel electrophoresis described by P. O'Farrel with isoelectric point plotted against molecular mass. All major erythrocyte proteins, including high molecular weight proteins, such as spectrin and band 3 protein, identified by one-dimensional sodium dodecyl sulfate gel electrophoresis, were visualized by silver staining of two-dimensional gels. All in all about 50 polypeptides were distinguished on two-dimensional electrophoretic patterns. Preliminary protein map was developed.     

Translation of murine leukemia virus RNA in cell-free systems from animal cells.

The virion RNA of Moloney murine leukemia virus (MuLV) has been translated in eukaryotic cell-free systems derived from mouse L- and human HeLa cells. In both systems at least three polypeptides, approximately 60,000, 70,000, and 180,000 in apparent molecular weight, were formed in response to the added 35S MuLV RNA. All three polypeptides were precipitable with antiserum to detergent-disrupted MuLV. Fingerprint analysis of tryptic digests indicated that all three contain anino acid sequences in common with each other and with the major methionine-containing structural proteins of the virion.     

Preparative scale, high resolution purification of low molecular weight DNA fragments

A commercially available continuous electroelution system has been used to separate and purify low molecular weight DNA fragments from polyacrylamide gels. This method has several advantages over previously reported methods for the recovery of DNA fragments from polyacrylamide gels. This technique, which gives very high recovery rates (80-95%), can be carried out on a relatively large scale and in a way that is not labour intensive. Data are presented for the purification of DNA fragments with molecular weights in the range 1-4 x 10(5) (200-700 base-pairs), although the method is also applicable to larger molecular weight DNA fragments, RNAs and proteins.     

Correlated induction of nitrate uptake and membrane polypeptides in corn roots

Induction of corn (Zea mays L.) seedling root membrane polypeptides was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis in relation to induction of nitrate uptake. When nitrate uptake was studied using freshly harvested roots from 4-day old corn seedlings, a steady state rate of uptake was achieved after a lag of 2 to 3 hours. The plasma membrane fraction from freshly harvested roots (uninduced) and roots pretreated in 5 millimolar nitrate for 2.5 or 5 hours (induced) showed no differences in the major polypeptides with Coomassie blue staining. Autoradiography of the ³⁵S-methionine labeled proteins, however, showed four polypeptides with approximate molecular masses of 165, 95, 70, and 40 kilodaltons as being induced by both 2.5 and 5-hour pretreatment in 5 millimolar nitrate. All four polypeptides appeared to be integral membrane proteins as shown by Triton X-114 (octylphenoxypolyethoxyethanol) washing of the membrane vesicles. Autoradiography of the two-dimensional gels revealed that several additional low molecular weight proteins were induced. A 5-hour pretreatment in 5 millimolar chloride also induced several of the low molecular weight polypeptides, although a polypeptide of about 30 kilodaltons and a group of polypeptides around 40 kilodaltons appeared to be specifically induced by nitrate. The results are discussed in relation to the possibility that some of the polypeptides induced by nitrate treatment may be directly involved in nitrate transport through the plasma membrane.     

Pupal and larval cuticle proteins of Drosophila melanogaster

Proteins, soluble in 7 M urea, were extracted from third-instar larval and pupal cuticles of Drosophila melanogaster. Both extracts contain a limited number of polypeptides resolved by one- or two-dimensional electrophoresis. The five major larval proteins have low molecular weights (less than 20000) and are not glycosylated. The major pupal cuticle proteins fall into two size classes: two with apparent molecular weights of 56K and 82K and four with molecular weights between 15K and 25K. The proteins with high apparent molecular weights are glycosylated. In nondenaturing gels, no components of the larval and pupal cuticle extracts comigrate. One-dimensional "fingerprints" indicate that cuticle proteins from these two stages have unique primary structures. Immunological results indicate that the major low molecular weight larval and pupal cuticle proteins are comprised of two families of proteins that share antigenic determinants. The high molecular weight pupal cuticle proteins are immunologically unrelated to the low molecular weight components. We conclude that the pupal and larval proteins are encoded in part by multigene families that have arisen by gene duplication and evolutionary divergence.     

Isolation and characterization of an extremely basic protein from adenovirus type 5.

By starch-gel electrophoresis and a staining method that is highly sensitive for argininyl residues, adenovirus type 5 was found to contain two minor basic polypeptides of extreme cathodic mobility in addition to the two known core proteins. The fastest-migrating polypeptide, named mu protein, and the second fastest polypeptide are found in adenovirions and virus-infected KB cells but not in top components or in uninfected cells. The top components and infected cells contain an additional basic polypeptide, presumably P-VII, that migrates slightly slower than polypeptide VII. None of the basic polypeptides of adenovirions was electrophoretically identical to the host histone. The basic proteins of adenovirions were purified by urea phosphocellulose column chromatography and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two minor basic core proteins, mu and another component, have similar mobilities in sodium dodecyl sulfate-polyacrylamide gels as a complex of polypeptides X-XII. After further purification on a Sephadex G-75 column, the mu protein was found to have a molecular weight of about 4,000. Amino acid analysis showed that the mu protein lacks tryptophan and 69% of the total amino acid residues are basic, that is, 54% arginine, 13% histidine, and 2% lysine. Only eight amino acids seem to contribute to make the mu polypeptide. There are 125 copies of the mu polypeptide per 1,000 copies of polypeptide VII in a virion.     

Polypeptide composition of purified QH2:cytochrome c oxidoreductase from beef-heart mitochondria

1. The polypeptide composition of purified QH₂:cytochrome c oxidoreductase prepared by three different methods from beef-heart mitochondria has been determined. Polyacrylamide gel electrophoresis in the presence of dodecyl sulphate resolves eight intrinsic polypeptide bands; when, in addition, 8 M urea is present and a more highly cross-linked gel is used, the smallest polypeptide band is resolved into three different bands.

2. The identity of several polypeptide bands has been established by fractionation. The two heaviest polypeptides (bands 1 and 2) represent the so-called core proteins, band 3 the hemoprotein of cytochrome b, band 4 the hemoprotein of cytochrome c₁, band 5 the Rieske Fe-S protein, band 6 a polypeptide associated with cytochrome c₁ and identified with the so-called oxidation factor, and band 7 a polypeptide associated with cytochrome b.

3. The validity of molecular weight estimates for the polypeptides of the enzyme based on their mobility on dodecyl sulphate gels has been examined. The polypeptides of bands 1, 2 and 3 showed anomalous migration rates. The molecular weights of the other polypeptides have been estimated from their relative mobilities on either dodecyl sulphate gels or 8 M urea-dodecyl sulphate gels as 29 000, 24 000, 12 000, 8000, 6000, 5000 and 4000, respectively.

4. The stoicheiometry of the different polypeptides in the intact complex was determined using separate staining factors for the individual polypeptide bands.