Gramicidin S-synthetase. Electrophoretic characterization of the multienzyme.

1. A method characterizing the fully active gramicidin S-synthetase (EC. 6.3.2.-) multienzyme in protein mixtures by a combination of sedimentation and polyacrylamide gel electrophoretic mobility data has been described. 2. The molecular weight of 280000 has been reevaluated by gradient centrifugation, gel filtration, and polyacrylamide gel electrophoresis in presence of sodium dodecyl sulfate. The size of the multienzyme is not changed by sodium dodecyl sulfate treatment. 3. In polyacrylamide gel electrophoresis dimerisation occurs in Tris, while two bands, which may represent monomer and dimer, are observed in phosphate. 4. Reliability of molecular weight determinations of sodium dodecyl sulfate-protein complexes of sizes up to 300000 daltons has been determined, correlating either mobilities or retardation coefficients.     

Plasmid-mediated quinolone resistance in pseudomonas putida isolates from imported shrimp

Fourteen quinolone-resistant Pseudomonas putida isolates were recovered from imported frozen shrimp sold in the United States. Two isolates harbored plasmids with qnrA and qnrB genes. PCR and DNA sequencing of quinolone resistance-determining regions identified novel substitutions in GyrA (His139→Glu and Thr128→Ala) and GyrB (Thr442→Asn, Gly470→Ala, and Ile487→Pro) and previously reported substitutions in GyrB (Asp489→Glu) and ParC (Thr105→Pro).     

Charge separation of proteins complexed with sodium dodecyl sulfate by acid gel electrophoresis in the presence of cetyltrimethylammonium bromide.

Globular proteins, casein, and membrane proteins which were reacted with sodium dodecyl sulfate were studied by acid urea gel electrophoresis. The sodium dodecyl sulfate bound tightly to the proteins, producing a more acidic charge which prevented migration into the gel. When cetyltrimethylammonium bromide was added to the sodium dodecyl sulfate-protein complexes, the sodium dodecyl sulfate apparently reacted with cetyltrimethylammonium bromide and dissociated so that the proteins migrated in acid gel in a normal manner as compared to the proteins without any added detergent. The sodium dodecyl sulfate-cetyltrimethylammonium bromide complex could be removed from the proteins by centrifugation. Thus, cetyltrimethylammonium bromide used in conjunction with acid gel electrophoresis allows direct comparison by charge of proteins fractionated in the presence of sodium dodecyl sulfate with the starting mixture of proteins not exposed to detergent. The reaction of cetyltrimethylammonium bromide with sodium dodecyl sulfate in acidic urea also provides a simple convenient method of removal of sodium dodecyl sulfate from proteins.     

Cell-free synthesis of phytochrome apoprotein

A single polypeptide is immunospecifically precipitated by monospecific antiphytochrome from the total translation products of both wheat-germ and rabbit-reticulocyte cell-free protein synthesizing systems programmed with oat (Avena sativa L.) poly(A) RNA. The mobility of this polypeptide is slightly lower on sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis than that of immunoaffinity-purified, 118 kdalton phytochrome and corresponds to an apparent molecular weight of 124 kdalton. Evidence against the possibility that this mobility difference results from intracellular processing of the 124-kdalton protein is provided by extraction of freeze-dried tissue directly into boiling SDS-containing buffer. This procedure yields a phytochrome species with a mobility on SDS polyacrylamide gel electrophoresis indistinguishable from that of the in-vitro translation product. Together the data indicate that the phytochrome polypeptide is synthesized in its mature form in the cell but is subject to modification to a form with lower apparent molecular weight during immunopurification.Abbreviations IgG immunoglobulin G - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Isolation and certain properties of minor protein P55 inhibiting myosin and actinomyosin ATPase activity

A method of minor protein P55 isolation from extract of soluble proteins of A-zone of the sarcomere from rabbit skeletal muscle is described. It is shown that this protein inhibits Ca2+-ATPase of myosin and Mg2+-ATPase of reconstructed actomyosin, but it does not affect superprecipitation of actomyosin. The molecular weight which is determined by mobility and its polypeptide chain polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate is about 35 000 dalton.     

Outer membrane of Pseudomonas aeruginosa: heat- 2-mercaptoethanol-modifiable proteins.

A number of polyacrylamide gel systems and solubilization procedures were studied to define the number and nature of "major" polypeptide bands in the outer membrane of Pseudomonas aeruginosa. It was shown that five of the eight major outer membrane proteins were "heat modifiable" in that their mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was determined by the solubilization temperature. Four of these heat-modifiable proteins had characteristics similar to protein II of the Escherichia coli outer membrane. Addition of lipopolysaccharide subsequent to solubilization caused reversal of the heat modification. The other heat-modifiable protein, the porin protein F, was unusually stable to sodium dodecyl sulfate. Long periods of boiling in sodium dodecyl sulfate were required to cause conversion to the heat-modified form. This was demonstrated both with outer membrane-associated and purified lipopolysaccharide-depleted protein F. Furthermore, lipopolysaccharide treatment had no effect on the mobility of heat-modified protein F. Thus it is concluded that protein F represents a new class of heat-modifiable protein. It was further demonstrated that the electrophoretic mobility of protein F was modified by 2-mercaptoethanol and that the 2-mercaptoethanol and heat modification of mobility were independent of one another. The optimal conditions for the examination of the outer membrane proteins of P. aeruginosa by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis are discussed.     

A study of the single polypeptide nature of rhodanese. A comparison of different preparations.

The enzyme rhodanese (EC 2.8.1.1) appears as a single polypeptide chain protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of this species is approx. 33 000. This contrasts with previous reports that rhodanese behaves on gel filtration chromatography as a rapidly equilibrating monomer-dimer system composed of identical subunits with a molecular weight of 18 500. We have investigated this apparent discrepancy by isolating the enzyme by the two different preparative procedures used in the above investigations. The two crystalline samples were subjected to gel filtration chromatography under a wide variety of conditions and to sodium dodecyl sulfate disc gel electrophoresis. The two preparations yielded rhodanese which behaved identically and no evidence for the monomeric species was obtained under any experimental condition tested. Thin-layer gel chromatography of clarified liver homogenates gave no evidence of rhodanese species other than that present in the purified samples. The variation in molecular weights observed in gel filtration chromatography may be a reflection of the conformational mobility of the enzyme leading to solvent-dependent changes in Stokes radius. If rhodanese is dimeric, special interactions must stabilize it under the conditions tested here.     

Expression and site-specific mutagenesis of phospholamban. Studies of residues involved in phosphorylation and pentamer formation

Full-length cDNAs encoding either dog cardiac or rabbit skeletal muscle phospholamban were expressed transiently in COS-1 cells. The expressed protein displayed the mobility of a pentamer when dissolved in sodium dodecyl sulfate and separated in polyacrylamide gels, and of a monomer when boiled prior to polyacrylamide gel separation. Site-specific mutagenesis was used to analyze the roles of several amino acids in the structure and function of the protein. Ser16 and Thr17 were shown to be phosphorylated uniquely by cAMP- and calmodulin-dependent protein kinases, respectively, confirming earlier observations on the native protein (Simmerman, H. K. B., Collins, J. H., Theibert, J.L., Wegener, A.D., and Jones, L.R. (1986) J. Biol. Chem. 261, 13333-13341). Arg13 and Arg14 were shown to be essential for both types of phosphorylation, and Arg9 was shown to be essential for calmodulin-dependent phosphorylation. In studies of pentamer stability, mutation of Gln22-Gln23 to Ala-Ala or Glu-Glu, of Gln26-Asn27 to Glu-Asp, or of Gln29-Asn30 to Glu-Asp had no effect on thermal stability of the pentamer, suggesting that hydrogen bonding involving these residues in domain IB is not important for pentamer stability. By contrast, mutation of Cys36, Cys41, and Cys46 in transmembrane domain II to Ser, Ala, or Phe diminished the stability of the pentamer when microsomal proteins were dissociated in sodium dodecyl sulfate and separated by polyacrylamide gel electrophoresis. In particular, the Cys41 to Phe mutant existed as a monomer at ambient temperature. These results suggest that the intramembranous cysteine residues are important for pentamer formation even though they are not disulfide-bonded.     

Isolation and characterization of bovine factor VII.

Factor VII (proconvertin) has been purified approximately 5 x 10(5)-fold from bovine plasma with an overall yield of 30%. The isolation procedure involves barium sulfate adsorption and elution, DEAE-Sephadex batchwise adsorption and elution, benzamidine-agarose column chromatography, heparin-agarose column chromatography, and preparative polyacrylamide gel disc electrophoresis. The final product was homogeneous when examined by gel electrophoresis in the presence of sodium dodecyl sulfate. A minimal molecular weight of 45,500 was determined by sedimentation equilibrium. The molecular weight estimated by sodium dodecyl sulfate gel electrophoresis was 54,000. Factor VII is composed of a single polypeptide chain possessing an amino-terminal sequence of Ala-Asn-Gly-Phe-Leu-. The amino acid and carbohydrate compositions of factor VII are also reported.     

Electrophoretic Analysis of Myelin Proteolipid Protein and Its Deacylated Form

Myelin proteolipid protein is known to contain covalently bound fatty acid. To determine the contribution of the fatty acid to the multiple bands observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the electrophoretic parameters of the proteolipid protein were compared with those of the deacylated form. The relative mobility and proportion of each band, as well as the retardation coefficient and free electrophoretic mobility, were not altered by removal of the fatty acid moiety. Furthermore, the acylated and deacylated forms bound the same amounts of sodium dodecyl sulfate. These data demonstrate that the presence of covalently bound fatty acids does not account for the electrophoretic heterogeneity of the proteolipid.     

Structure of the oligosaccharide of human J chain.

The complete structure of the oligosaccharide moiety of J chain isolated from a Waldenstr?ms macroglobulin Wa has been established. The oligosaccharide is present in three forms differing in the amount of sialic acid and designated J-A, J-B, and J-C. The structure and proportion of each of these is: formula : (see text) : Removal of the oligosaccharide moiety with glycosidases results in an increased mobility of J chain in sodium dodecyl sulfate polyacrylamide gel electrophoresis corresponding to a shift in apparent molecular weight from 23,500 to 19,500. The preparation and utilization of iodinated glycopeptides for sequence analysis is presented.     

Detection of iron-sulfur center-containing subunits of mitochondrial NADH dehydrogenase by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by high-performance gel permeation chromatography

Soluble NADH dehydrogenase resolved from Complex I of the mitochondrial electron-transfer chain was subjected to gel electrophoresis in the presence of sodium dodecyl sulfate at 4 degrees C, and then the gel was stained for iron with bathophenanthroline disulfonate and thioglycolic acid. The 23,000-dalton subunit was markedly stained, and the 51,000-dalton subunit was also stained, but only slightly. High-performance gel permeation chromatography using an eluant containing 0.1% sodium dodecyl sulfate also demonstrated that these subunits contain an iron-sulfur center: the elution pattern recorded by light absorption at 400 nm gave two peaks corresponding to the positions of the subunits.     

Purification and properties of an endothelial cell growth factor from human platelets

An endothelial cell growth factor has been purified about 1,000,000-fold to homogeneity from human platelets by a seven-step procedure. The purified product has an apparent Mr on sodium dodecyl sulfate-polyacrylamide gels of 45,000. The mobility in sodium dodecyl sulfate gel electrophoresis was similar in the presence or absence of reducing agents, indicating that the factor consists of a single polypeptide chain. Maximal stimulation by the purified protein was achieved at a concentration of about 20 ng/ml (440 pM). Heparin did not potentiate the activity, nor did the factor bind to heparin immobilized on Sepharose. The purified factor was heat- and acid-labile; it was active on porcine and human endothelial cells, but not on human foreskin fibroblasts. Chromatofocusing revealed that the pI of the factor was 4.6. The structural and functional characteristics of the platelet-derived endothelial cell growth factor are distinct from previously characterized endothelial cell mitogens with affinities for heparin.     

Production and functional analysis of normal and variant recombinant human transthyretin proteins.

The most common form of hereditary systemic amyloidosis is familial amyloidotic polyneuropathy associated with single amino acid changes in the plasma protein, transthyretin. In addition, there are two variants of transthyretin (Ser6 and Thr109) not associated with familial amyloidotic polyneuropathy but with familial euthyroid hyperthyroxinemia, also an autosomal dominant disorder. In these autosomal dominant diseases, most affected individuals are heterozygous and therefore have hybrid forms of the tetrameric plasma transthyretin. In order to study the structure/function relationships of homozygous variant transthyretins, normal human transthyretin and five variant transthyretins (Gly6----Ser, Leu58----His, Thr60----Ala, Ile84----Ser, and Ala109----Thr) were produced in Escherichia coli using the expression vector, pCZ11, and site-directed mutagenesis. These recombinant transthyretin (r-TTR) proteins showed the correct size (14 kilodaltons) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western analysis and self-associated into tetramers as determined by size exclusion chromatography. Recombinant normal, Ser6, and Ala60 r-TTRs had an affinity for thyroxine indistinguishable from normal human TTR purified from plasma, whereas His58 and Ser84 r-TTRs had significantly reduced affinity. On the other hand, Thr109 r-TTR had a much higher affinity, probably due to its position within the thyroxine-binding pocket. Expression of mutant transthyretins in E. coli provides the opportunity to study structure/function relationships and amyloid-forming capabilities induced by single amino acid substitutions in the transthyretin molecule.     

Purification,characterization, and action-pattern studies on the endo-(1 → 3)-β-d-glucanase from Rhizopus arrhizus QM 1032

The extracellular (1 → 3)-β-d-glucanase [1 → 3)-β-d-glucan glucanohydrolase, EC 3.2.1.6] produced by Rhizopus arrhizus QM 1032 was purified 305-fold in 70% overall yield. This preparation was found to be homogeneous by ultracentrifugation (sedimentation velocity and studies), electrophoresis on acrylamide gel with normal, sodium dodecyl sulfate, and urea-acetic acid gels, and upon isoelectric focusing. The amino acid composition of the enzyme has been determined and it possesses a carbohydrate moiety composed of mannose and galactose (in the ratio ≈5:1) that is linked to the protein through a 2-acetamido-2-deoxyglucose residue. The molecular number was confirmed by electrophoresis on gels of sodium dodecyl sulfate. The enzyme does not posses subunit structure. It hydrolyzes it substrates with retention of configuration and possesses transglycosylating ability. The rates of hydrolysis of a wide variety of substrates were determined, and its action pattern on a series of oligosaccharides containing mized (1 → 3-, (1 → 4)-, and (1 → 6)-β-d-glucopyranosyl residues was investigated. The enzyme favors stretches of β-d-(1 → 3) linkages, but it can hydrolyze β-d-(1 → 4) linkages that are flanked on the non-reducing side with stretches of β-d-(1 → 3) links. The enzyme will not act on (1 → 6)-β-d-glucosyl linkages located in stretches of β-d-(1 → 3) and will not act on (1 → 3) β-d-glycosidic linkages involving sugars other than d-glucose.     

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of bovine serum albumin oligomers produced by lipid peroxidation.

The oligomers of bovine serum albumin were produced by controlled reaction with peroxidizing linoleic acid to examine their possible utility as calibration proteins insodium dodecyl sulfate-polyacrylamide gel electrophoresis. The polymerization was effected in reaction mixtures containing linoleic acid undergoing peroxidation in the presence of ascorbic acid, and conditions that yield soluble oligomers with a wide molecular weight distribution were established. The interaction of these soluble oligomers with sodium dodecyl sulfate exhibited a binding isotherm indistinguishable from that obtained with bovine serum albumin. Furthermore, sodium dodecy sulfate-polyacrylamide gel electrophoresis of the albumin oligomers conformed to the empirical relation of molecular weight to mobility that pertains to the use of these oligomers as standard molecular weight markers.     

Purification and partial characterization of a plasma inhibitor of tonin

A plasma inhibitor of tonin activity in the rat, was purified by ammonium sulfate precipitation, ion-exchange of chromatography, and gel filtration. Its purity was investigated by analytical electrophoresis on polyacrylamide gel and by ultracentrifugation sedimentation velocity. The molecular weight (360 000) of the purified inhibitor was determined by sodium dodecyl sulfate electrophoresis and its isoelectric point (4.5) by gel isoelectrofocusing. The Stokes radius (640 nm) was evaluated by gel filtration studies and a frictional ratio (f/fo) of 1.95 was calculated from the molecular weight and Stokes radius. Kinetic studies using angiotensin I as substrate showed that the inhibition of tonin by the purified inhibitor was noncompetitive and does not exceed 70%. Electrophoresis showed the same mobility for [125I]tonin bound to plasma proteins and for [125I]tonin bound to the purified inhibitor. The inhibitor may be a protein resembling half of the dimeric protease inhibitor rat alpha 1-macroglobulin or human alpha 2-macroglobulin.     

Neurospora crassa mitochondria contain two forms of a 4'-phosphopantetheine-modified protein

When Neurospora crassa was labeled with [14C]pantothenic acid during growth, the mitochondrial fraction contained two bands of radioactivity of Mr 19,000 and 22,000 by sodium dodecyl sulfate gel electrophoresis. The 19-kDa band was converted to the 22-kDa band by four treatments which are characteristic of the cleavage of a thioester bond: dithiothreitol and 2-mercaptoethanol at basic but not neutral pH, alkaline methanolysis, sodium borohydride in tetrahydrofuran, and hydroxylamine at neutral pH. Mitochondrial subfractionation indicated that the 22-kDa form was preferentially associated with the soluble fraction while the 19-kDa form was found in all fractions. Several properties of the mitochondrial protein were similar to the Escherichia coli acyl carrier protein: Mr on sodium dodecyl sulfate gels, decreased electrophoretic mobility under deacylating conditions, isoelectric point, and covalent attachment of 4'-phosphopantetheine. The 19- and 22-kDa bands may therefore represent acylated and deacylated forms of a mitochondrial acyl carrier protein.     

Two-dimensional polyacrylamide gel electrophoresis of ribosomal proteins: improved resolution with Triton X-100

The nonionic detergent Triton X-100 binds in varying proportions to specific ribosomal proteins and decreases the relative mobility of these proteins during electrophoresis. When Triton X-100 binds to these ribosomal proteins in the first-dimension gel, the resolution of the ribosomal proteins in the second-dimension gel pattern is greatly improved. Maximum binding of Triton X-100 to the ribosomal proteins is dependent on pH, urea concentration, and the complete reduction of cysteine and methionine. After first-dimension electrophoresis the Triton X-100 in the gel does not interfere with the binding of sodium dodecyl sulfate to the ribosomal proteins and the molecular weight of these proteins can still be estimated directly from the second-dimension slab gel.     

Immunological detection of specific proteins in total cell extracts by fractionation in gels and transfer to diazophenylthioether paper

We describe a sensitive immunological procedure for the detection of specific proteins in total cell extracts and for the comparison of antigenically related polypeptides. Proteins are fractionated in polyacrylamide gels and transferred electrophoretically to diazophenylthioether paper, to which they bind covalently. Specific proteins are identified by incubation with specific antibody and 125 I-labeled protein A from Staphylococcus aureus, followed by autoradiography. High-resolution separation of proteins prior to transfer is achieved by polyacrylamide gradient gel electrophoresis in the presence of sodium dodecyl sulfate or by nonequilibrium pH gradient electrophoresis, followed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Further information can be obtained by limited enzymatic proteolysis of the proteins in the gel following polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and analysis of the cleavage products by gel electrophoresis at right angles to the first gel. We show the application of this technique to the detection and comparison in extracts from infected cells of proteins related immunologically to the simian virus 40 capsid proteins VP1 and VP3.