Isolation and characterization of the lipopolysaccharides from Bradyrhizobium japonicum.

The lipopolysaccharide (LPS) of Bradyrhizobium japonicum 61A123 was isolated and partially characterized. Phenol-water extraction of strain 61A123 yielded LPS exclusively in the phenol phase. The water phase contained low-molecular-weight glucans and extracellular or capsular polysaccharides. The LPSs from B. japonicum 61A76, 61A135, and 61A101C were also extracted exclusively into the phenol phase. The LPSs from strain USDA 110 and its Nod- mutant HS123 were found in both the phenol and water phases. The LPS from strain 61A123 was further characterized by polyacrylamide gel electrophoresis, composition analysis, and 1H and 13C nuclear magnetic resonance spectroscopy. Analysis of the LPS by polyacrylamide gel electrophoresis showed that it was present in both high- and low-molecular-weight forms (LPS I and LPS II, respectively). Composition analysis was also performed on the isolated lipid A and polysaccharide portions of the LPS, which were purified by mild acid hydrolysis and gel filtration chromatography. The major components of the polysaccharide portion were fucose, fucosamine, glucose, and mannose. The intact LPS had small amounts of 2-keto-3-deoxyoctulosonic acid. Other minor components were quinovosamine, glucosamine, 4-O-methylmannose, heptose, and 2,3-diamino-2,3-dideoxyhexose. The lipid A portion of the LPS contained 2,3-diamino-2,3-dideoxyhexose as the only sugar component. The major fatty acids were beta-hydroxymyristic, lauric, and oleic acids. A long-chain fatty acid, 27-hydroxyoctacosanoic acid, was also present in this lipid A. Separation and analysis of LPS I and LPS II indicated that glucose, mannose, 4-O-methylmannose, and small amounts of 2,2-diamino-2,3-dideozyhexose and heptose were components of the core region of the LPS, whereas fucose, fucosmine, mannose, and small amounts of quinovosamine and glucosamine were components of the LPS O-chain region.     

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 characterization of a major outer membrane protein of Pseudomonas aeruginosa. Evidence for the occurrence of a lipoprotein.

In the outer membrane of P. aeruginosa, a protein of apparent molecular weight 8,000 (protein I) is present as a major protein. Purification and chemical analysis of protein I were carried out. This protein was purified by essentially the same procedure as for the purification of the E. coli lipoprotein, which was developed by Inouye et al. (J. Bacteriol. (1976) 127, 555--563). The amino acid composition of protein I was determined. Protein I lacks proline, valine, isoleucine, phenylalanine, tryptophan, and half-cystine. Fatty acid analysis of the protein revealed that it contained 0.89 mol of fatty acids per mol of protein. Among the fatty acids hexadecanoic acid (C16:0) was predominant. In an in vivo labeling experiment, [2-3H]glycerol was incorporated into protein I. A protein with similar mobility to protein I on urea-SDS polyacrylamide gel electrophoresis was isolated from the purified peptidoglycan of P. aeruginosa by trypsin digestion. The amino acid composition of this protein was essentially the same as that of protein I. These results indicate that the outer membrane of P. aeruginosa contains a protein analogous to the E. coli lipoprotein, although considerable differences were observed in the amino acid composition and the fatty acid content.     

Chemical and immunological characterization of lipopolysaccharides from phase I and phase II Coxiella burnetii.

Lipopolysaccharides (LPSs) isolated from phase I and phase II Coxiella burnetii (LPS I and LPS II, respectively) were analyzed for chemical compositions, molecular heterogeneity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunological properties. The yields of crude phenol-water extracts from phase I cells were roughly three to six times higher than those from phase II cells. Purification of LPSs by ultracentrifugation gave similar yields for both LPS I and LPS II. Purified LPS I and LPS II contained roughly 0.8 and 0.6% protein, respectively. The fatty acid constituents of the LPSs were different in composition and content, with branched-chain fatty acids representing about 15% of the total. beta-Hydroxymyristic acid was not detected in either LPS I or LPS II. A thiobarbituric acid-periodate-positive compound was evident in the LPSs; however, this component was not identified as 3-deoxy-D-mannooctulosonic acid by gas and paper chromatographies. LPS II contained D-mannose, D-glucose, D-glyceromannoheptose, glucosamine, ethanolamine, 3-deoxy-D-mannooctulosonic acid-like material, phosphate, and fatty acids. LPS I contained the unique disaccharide galactosaminuronyl glucosamine and nine unidentified components in addition to the components of LPS II. The hydrophobic, putative lipid A fraction of LPS I and LPS II contained the above constituents, but the hydrophilic fraction was devoid of ethanolamine. The LPS I disaccharide galactosaminuronyl glucosamine was found in both fractions of the acetic acid hydrolysates. Analysis of LPSs by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by silver staining indicated that LPS II was composed of only one band, whereas LPS I consisted of six or more bands with irregular spacing. Ouchterlony immunodiffusion tests demonstrated that LPS I reacted with phase I but not with phase II whole-cell hyperimmune antibody, and LPS II reacted neither with phase I nor phase II hyperimmune antibody. From these results, it was concluded that the chemical structures of LPSs from C. burnetii were different from those of the LPSs of gram-negative bacteria; however, the LPS structural variation in C. burnetii may be similar to the smooth-to-rough mutational variation of saccharide chain length in gram-negative bacteria.     

Partial characterization of oat and rye phytochrome

Purified oat and rye phytochrome were examined by analytical gel chromatography, polyacrylamide gel electrophoresis, N-terminal, and amino acid analysis. Purified oat phytochrome had a partition coefficient on Sephadex G-200 (sigma(200)) of 0.350 with an estimated molecular weight of 62,000; sodium dodecyl sulfate polyacrylamide electrophoresis gave an equivalent weight estimate. Purified rye phytochrome had a sigma(200) value of 0.085 with an estimated molecular weight of 375,000; sodium dodecyl sulfate electrophoresis gave a weight estimate of 120,000, indicating a multimer structure for the nondenatured protein. Comparative sodium dodecyl sulfate electrophoresis with purified phycocyanin and allophycocyanin gave a molecular weight estimate of 15,000 for allophycocyanin, and two constituent classes of subunits for phycocyanin with molecular weights of 17,000 and 15,000. Amino acid analysis of oat phytochrome confirmed a previous report; amino acid analysis of rye phytochrome differs markedly from a previous report. Oat phytochome has four detectable N-terminal residues (glutamic acid, serine, lysine, and leucine, or isoleucine); rye phytochrome has two detectable groups (aspartic and glutamic acids). Model experiments subjecting purified rye phytochrome to proteinolysis generate a product with the characteristic spectral and weight properties of oat phytochrome, as it has been described in the literature. It is concluded that the structural characteristics of purified rye phytochrome are likely those of the native protein.     

Isolation and characterization of N-long chain acyl aminoacylase from Pseudomonas diminuta

N-Long chain acyl aminoacylase II (Enzyme II) catalyzing the hydrolysis of N-long chain acyl amino acids was purified about 2,000-fold from the cell extracts of Pseudomonas diminuta with 1.8% of activity yield. The purified enzyme was homogeneous on polyacrylamide gel electrophoresis and the molecular weight was 220,000. Enzyme II differed from N-long chain acyl aminoacylase I (Enzyme I) in molecular weight, in substrate specificity, and in behavior toward temperature and pH. Enzyme II showed broader substrate specificity than Enzyme I and catalyzed the hydrolysis of lipoamino acids containing various amino acid residues, although Enzyme I was almost specific to the lipoamino acids containing L-glutamate. The extent of hydrolysis by Enzyme II reaction varied depending on the kinds of lipoamino acids and were: 100% for palmitoyl-L-glutamate, 91% for myristoyl-L-glutamate, 85% for lauroyl-L-glutamate, 54% for lauroyl-L-aspartate, 28% for stearoyl-L-glutamate and 17.5% for lauroyl-glycine.     

Multiple forms of myeloperoxidase from human neutrophilic granulocytes: evidence for differences in compartmentalization, enzymatic activity, and subunit structure

Multiple forms of myeloperoxidase from normal human neutrophilic granulocytes obtained from a single donor can be resolved by carboxymethyl (CM)-cellulose ion-exchange column chromatography into three forms (I, II, and III) designated in order of elution of adsorbed enzyme using a linear salt gradient. Selective solubilization of individual forms of the enzyme by detergent (form I) or high-ionic-strength procedures (forms II and III) suggested that these forms of the enzyme were compartmentalized differently. All three forms were purified by a combination of preferential extraction, manipulation of ionic strength, and ion-exchange and molecular sieve chromatography. Purified forms II and III had similar specific activities for a variety of substrates. Form I was less active toward several of these same substrates, most notably iodide, with a specific activity about one-half that of forms II and III. All forms had similar spectral properties characteristic of a type alpha heme. The amino acid compositions of the three forms were similar, yet significant differences were found in selected residues such as the charged amino acids. Native polyacrylamide gel electrophoresis resolved small differences in mobility between the forms which were consistent with the charge heterogeneity observed on CM-cellulose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis data were consistent with the generally accepted subunit structure of two heavy chains and two light chains. All three forms contained a small-molecular-weight subunit of Mr 11,500. Form I contained a large subunit of Mr 63,000, while forms II and III contained a corresponding subunit of Mr approximately 57,500. We conclude that heterogeneity of human myeloperoxidase is accompanied by differences in cellular compartmentalization, enzymatic activity, and subunit structure.     

Some molecular properties of asparagine synthetase from rat liver

Asparagine synthetase purified from rat liver reveals two species (slower migrating band I and faster migrating band II) when subjected to polyacrylamide gel electrophoresis under nondenaturing conditions (S. Hongo and T. Sato (1981) Anal. Biochem. 114, 163-166). We have investigated some molecular properties of these species. Elution of band I from the gel and re-electrophoresis showed that band I yielded band II similar to that of the initial run. Peptide maps by limited proteolysis were very similar and amino acid compositions were also alike in the two species. L-Lysine was identified as the sole NH2-terminal amino acid in both the species. By cross-linking experiments the enzyme was shown to be a dimeric protein. When the purified enzyme was subjected to isoelectric focusing the enzyme activity and protein focused at pH 6.0 in a single peak. These results demonstrate that rat liver asparagine synthetase is composed of two identical subunits. The enzyme, inactivated by storage at -20 degrees C for about 3 months, showed aggregated forms in polyacrylamide gel electrophoresis, and was reactivated markedly by the addition of dithiothreitol.     

Water buffalo (Bubalus bubalis) hemoglobins: an electrophoretic and chromatographic study

1. Hemoglobins from three phenotypes of Italian water buffalo (Bubalus bubalis), named AA, AB and BB, were selected by starch gel electrophoresis at alkaline pH and analyzed using polyacrylamide gel isoelectric focusing and subsequent analysis of titration curves to reveal differences between two types of hemoglobin identified as Hb fast and Hb slow. 2. Globins from Hb fast and Hb slow were purified by fast protein liquid chromatography (FPLC). Electrophoretic differences were found in the respective alpha-chains using polyacrylamide gel disc-electrophoresis at acid pH, polyacrylamide gel isoelectric focusing and by subsequently analyzing titration curves. 3. The results suggest that the alpha chains of Hb fast and Hb slow, called I alpha and II alpha, respectively, differ in at least two aminoacid residues. Subsequently, these amino acids were identified as lysine and cysteine.     

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.     

Cytochrome c oxidase from bakers' yeast. III. Physical characterization of isolated subunits and chemical evidence for two different classes of polypeptides.

Earlier studies have shown that cytochrome c oxidase from bakers' yeast is an oligomeric enzyme which contains three polypeptides (I to III) synthesized on mitochondrial ribosomes and four polypeptides (IV to VII) synthesized on cytoplasmic ribosomes. These polypeptide subunits have now been isolated by a simple protocol which utilizes differences in polypeptide charge, solubility, and size. Their molecular weights determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, gel filtration in the presence of guanidine hydrochloride, and amino acid analysis were: I, 40,000; II, 33,000; III, 22,000; IV, 14,500; V, 12,700; VI, 12,700; and VII, 4,600. All seven polypeptide subunits exhibited acidic isoelectric points; cytoplasmically made subunits were more acidic than mitochondrially made ones. The amino acid composition of two mitochondrially made subunits and two cytoplasmically made subunits was determined. The two mitochondrial translation products, I and II, contained only 34.7% and 42.1% polar amino acids, respectively, whereas the two cytoplasmic translation products, IV and VI, contained 48.3% and 49.3%, respectively. This agreed with the observation that Subunits I and II are very insoluble, requiring detergents for solubility, whereas Subunits IV and VI are water-soluble in the absence of any added detergent. These results indicate that the cytochrome c oxidase subunits synthesized on mitochondrial and cytoplasmic ribosomes are fundamentally different in size, isoelectric properties, and hydrophobicity. They also suggest the possibility that at least some of the mitochondrially made subunits are buried in the lipid phase of the mitochondrial inner membrane.     

Highly acidic proteins from human brain: purification and properties of Glu-50 protein

Three extremely acidic proteins were isolated from human brain and purified to apparent homogeneity. One of them, Glu-50 protein, contained much glutamic acid (about 50% of the total amino acids). Its purification involved ammonium sulfate fractionation, DEAE-Sephadex A-50 chromatography, and gel filtration on Sephadex G-100 and G-75. Its molecular weight was determined to be 11,000 by SDS polyacrylamide gel electrophoresis and 34,000-36,000 by gel filtration on Sephadex G-75, suggesting that it consists of three identical polypeptide chains. Its isoelectric point was pH 3.9. Its N-terminal amino acid sequence was NH2-Asp-Glu-Pro-Pro-Asp-Glu and its C-terminal amino acid was Lys. It contained no detectable carbohydrate.     

Hydrolysis of plant cuticle by plant pathogens. Purification, amino acid composition, and molecular weight of two isozymes of cutinase and a nonspecific esterase from Fusarium solani f. pisi.

The extracellular fluid of the plant pathogen, Fusarium solani f. pisi, grown on the plant cuticular polymer, cutin, was shown to contain cutinase and p-nitrophenyl palmitate hydrolase activities (R.E. Purdy and P.E. Kolattukudy (1973), Arch. Biochem. Biophys. 159, 61). From this extracellular fluid two isozymes of cutinase and a nonspecific esterase (p-nitrophenyl palmitate hydrolase) were isolated using Sephedex G-100 gel filtration, QAE-Sephadex chromatography, and SE-Sephedex chromatography. Phenolics contained in the extracellular fluid were found to be associated with the cutinase but not with the nonspecific esterase, and the phenolic materials were removed from cutinase at the QAE-Sephedex step. A 34-fold purification of the nonspecific esterase and a 6.5-fold purification of cutinase were achieved by the procedure described. The two isozymes of cutinase (I and II) and the nonspecific esterase were homogeneous as judged by polyacrylamide disc gel electrophoresis and sedimentation equilibrium centrifugation. Molecular weights of cutinase I, cutinase II, and the nonspecific esterase were determined by Sephedex G-100 gel filtration, sedimentation equilibrium centrifugation, amino acid composition, and sodium dodecyl sulfate polyacrylamide disc gel electrophoresis. The values obtained with these techniques agreed with each other and were about 22,000 for both cutinases and 52,000 for the nonspecific esterase. The dodecyl sulfate gel electrophoresis indicated that a small portion of cutinase II contained proteolylic clips, near the middle of the polypeptide chain, and that the nonspecific esterase might also have undergone some proteolylic modification. The amino acid composition of cutinase I was similar to that of cutinase II except for the presence of a larger number of tryptophan residues in the latter, while the amino acid composition of the nonspecific esterase showed more differences from that of either cutinase.     

Isolation and chemical properties of multiple active principles from miracle fruit

The active principle of miracle fruit which modifies the taste of sour stimuli into a sweet taste was purified by electrofocusing and its chemical propeorties were determined. The electrofocusing resulted in separation of three species of the active proteins (I, II and III) whose isoelectric points were 9.3, 9.0 and 8.0, respectively. Application of three proteins to polyacrylamide gel electrophoresis gave single bands, respectively. All the proteins had the same molecular weight of 40 000–41 000. Essential difference was not found between amino acid compositions of these proteins. N-terminal amino acid residue of the three proteins was determined to be 16% (w/w) for protein I, 20% (w/w) for protein II and 41% (w/w) for protein III. Eight species of carbohydrates (l-fucose, d-mannose, d-galactose, d-glucose, d-xylose, l-arabinose, l-rhamnose and d-glucosamine) were identified by gas chromatography and amino acid analysis as being carbohydrate components of protein II, which was an abundant component, and their relative contents were determined. 1·10⁻⁸ M protein II was sufficient to induce the half-maximal sweet-inducing activity.     

Protein PSII-G. An additional component of photosystem II identified through its plastid gene in maize

An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DNA fragment Bam5 was sequenced. It encodes a protein which contains a high proportion of hydrophilic amino acids, of which 22% are hydroxylated, interrupted by hydrophobic domains. A synthetic peptide corresponding to a hydrophilic sequence was used to generate antibodies. Western blots of photosystem I and II complexes prepared from maize and spinach thylakoids indicate that the psbG gene product is a membrane-associated protein of the photosystem II complex that migrates as a 24-kDa species on polyacrylamide gel electrophoresis.     

ISOLATION OF AN ACID-SOLUBLE PROTEIN WITH LOW MOLECULAR WEIGHT FROM MONKEY BRAIN

Abstract— The isolation of a perchloric acid-soluble low molecular weight protein from brain of Macaca irus is reported. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and gel isoelectric focusing indicate that the protein is free of impurities. The molecular weight, as determined by gel filtration and sodium dodecyl sulphate gel electrophoresis, is shown to be 10,400 and 9900, respectively. This is in agreement with the value of 10,700 obtained from amino acid analysis. The protein contains 27 per cent acid amino acids and 15 per cent basic amino acids. However, the relatively high amide content gives the protein a neutral nature as shown by isoelectric point determination using gel isoelectric focusing.     

Multiple forms of rat dentin phosphoproteins

Previous studies have shown that the phosphoprotein from rat dentin is heterogenous and can be partially separated into two fractions by ion-exchange chromatography. These proteins were further characterized by polyacrylamide gel electrophoresis, gel chromatography, and amino acid and phosphate analysis, after chromatographic separations on ion-exchange columns. On 5-15% gradient gels, the phosphoproteins extracted from rat dentin and precipitated by CaCl2 gave three Alcian blue-staining bands with apparent molecular weights in the 90-95,000 range. The two slower-moving bands corresponded to highly phosphorylated proteins (HP) that had phosphoserine contents of greater than 400 residues per thousand and contained little or no valine, leucine, phenylalanine, or arginine. The faster-moving band corresponded to a moderately phosphorylated protein that contained about 250 residues per thousand of phosphoserine and greater quantities of glutamic acid, proline, and several other amino acids than HP. The nature of the phosphoproteins in HP was further studied after total removal of the phosphate with an insoluble form of bovine intestinal alkaline phosphatase. The dephosphorylated product (dP-HP) gave a single major band on gel electrophoresis but showed evidence for two closely related NH2-terminal sequences, Asp-Asp-Asp-Asn and Asp-Asp-Pro-Asn. The dephosphorylated material was separated into two components (dP-HP1 and dP-HP2) by chromatography on QAE-Sephadex A-25. The amino acid compositions of the two components showed that they differed in their primary structures. This conclusion was verified by the finding of the proline-containing sequence in dP-HP2. In addition to these two groups of phosphoproteins, a third class, LP, contains low levels of phosphoserine and high amounts of glutamic acid (W.T. Butler, M. Bhown, M.T. DiMuzio, and A. Linde, (1981) Coll. Res. 1, 187-199).     

Immunochemistry of phytochrome

Purified oat and rye phytochrome were examined by analytical gel chromatography, polyacrylamide gel electrophoresis, N-terminal, and amino acid analysis. Purified oat phytochrome had a partition coefficient on Sephadex G-200 (σ₂₀₀) of 0.350 with an estimated molecular weight of 62,000; sodium dodecyl sulfate polyacrylamide electrophoresis gave an equivalent weight estimate. Purified rye phytochrome had a σ₂₀₀ value of 0.085 with an estimated molecular weight of 375,000; sodium dodecyl sulfate electrophoresis gave a weight estimate of 120,000, indicating a multimer structure for the nondenatured protein. Comparative sodium dodecyl sulfate electrophoresis with purified phycocyanin and allophycocyanin gave a molecular weight estimate of 15,000 for allophycocyanin, and two constituent classes of subunits for phycocyanin with molecular weights of 17,000 and 15,000. Amino acid analysis of oat phytochrome confirmed a previous report; amino acid analysis of rye phytochrome differs markedly from a previous report. Oat phytochome has four detectable N-terminal residues (glutamic acid, serine, lysine, and leucine, or isoleucine); rye phytochrome has two detectable groups (aspartic and glutamic acids). Model experiments subjecting purified rye phytochrome to proteinolysis generate a product with the characteristic spectral and weight properties of oat phytochrome, as it has been described in the literature. It is concluded that the structural characteristics of purified rye phytochrome are likely those of the native protein.     

Purification and properties of the very high density lipoprotein from the hemolymph of adult Triatoma infestans

The very high density lipoprotein (VHDL) of Triatoma infestans hemolymph from adult males has been isolated and purified by two-step density gradient ultracentrifugation. It appears to be homogeneous as judged by native polyacrylamide gel electrophoresis. The content of VHDL in hemolymph was estimated to be 8 mg protein/ml. The purified protein has a molecular weight (Mr) of 450,000, is composed of six subunits of Mr approximately equal to 77,000, and possesses a high content of aromatic amino acids. This protein is glycosylated and contains 3% of lipids by weight with a remarkable amount of free fatty acids (25% of total lipids). The T. infestans VHDL has a different lipid and amino acid composition from lipophorin. The lipid composition and the spectroscopic studies using cis-parinaric acid indicated a high fatty acid binding affinity. It has nine binding sites per mol of VHDL. Competence studies revealed that VHDL has its highest affinity for the binding of palmitic acid followed by stearic and arachidonic acids.     

Purification and characterization of nucleoside diphosphate kinase from spinach leaves.

Two types of nucleoside diphosphate kinase (NDP kinase I and NDP kinase II) have been purified from spinach leaves to electrophoretic homogeneity. The enzymes were copurified with apparent [35S]GTP-gamma S-binding activities. NDP kinase I, which was not adsorbed to a hydroxyapatite column, and NDP kinase II, which was adsorbed, had molecular weights of 16,000 and 18,000, respectively, as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The molecular weights determined by gel filtration were 92,000 and 110,000, respectively, suggesting that both enzymes are composed of six identical subunits. Minor differences in some amino acids between NDP kinase I and NDP kinase II were observed when both enzymes were analyzed for amino acid composition. The apparent [35S]GTP gamma S-binding activity of purified NDP kinase I and NDP kinase II was found to be due to the formation of a [35S]thiophosphorylated enzyme, which is the intermediate of the NDP kinase reaction.