Phosphorylation of a sugar-specific protein component of the lactose transport system in Staphylococcus aureus

Structure and evolution of a multidomain multiphosphoryl transfer protein. Nucleotide sequence of the fruB(HI) gene in Rhodobacter capsulatus and comparisons with homologous genes from other organisms

The gene order of the fructose (fru) operon and nucleotide sequence of the first gene (fruB(HI) of Rhodobacter capsulatus are reported, analyzed and compared with homologous genes from other bacteria, and the gene products are identified. Included within the region reported is a gene encoding a multiphosphoryl transfer protein (MTP) of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). MTP consists of three moieties: a fructose-specific enzyme III (IIIfru)-like N-terminal moiety (residues 1 to 143) followed by an FPr(HPr)-like moiety (residues 157 to 245) and an enzyme I-like moiety (residues 273 to 827). The enzyme III-like moiety closely resembles the N-terminal 143 residues of the IIIfru-FPR fusion protein from Salmonella typhimurium (40.6% identity throughout its length) and the C-terminal 145 residues of the mannitol-specific enzyme II (IImtl) (37.8% identity throughout its length with the IIImtl moiety of IImtl). The FPr-like domain of MTP resembles the S. typhimurium FPr (42.4% identity) and the Escherichia coli or S. typhimurium HPr (38.8% identity). The enzyme I-like moiety resembles the E. coli enzyme I (38.9% identity). Predicted phosphorylation sites within the three functional units of MTP (His62 in the IIIfru-like moiety; His171 in the FPr-like moiety and His457 in the enzyme I-like moiety) were identified on the basis of sequence comparisons with the homologous proteins from enteric bacteria. The three functional domains of MTP are joined by two flexible "linkage" regions, rich in alanine, glycine and proline, which show 47% sequence identity with each other. They also exhibit a high degree of sequence identity with the linkage region of the mannose-specific enzyme III (IIIman) of the E. coli PTS as well as several other proteins of bacterial, eukaryotic and viral origin. At the RNA level, these linker regions formed hairpin structures with high (90%) G + C content. Analyses of the IIIfru-FPr fusion protein of S. typhimurium revealed that between the IIIfru and FPr moieties of this protein is a stretch of 142 amino acids that do not show homology to known PTS proteins. This region and the adjacent FPr-like region contain a sequence of 110 residues exhibiting 59% similarity to the receiver consensus motif defined by Kofoid and Parkinson. Because the Salmonella IIIfru-FPr fusion protein has been implicated in transcriptional regulation, this region of the Salmonella protein may prove to have regulatory significance.(ABSTRACT TRUNCATED AT 400 WORDS)

Cloning and expression of the beta-D-phosphogalactoside galactohydrolase gene of Lactobacillus casei in Escherichia coli K-12

Lactose metabolism in Lactobacillus casei 64H is associated with the presence of plasmid pLZ64. This plasmid determines both phosphoenolpyruvate-dependent phosphotransferase uptake of lactose and beta-D-phosphogalactoside galactohydrolase. A shotgun clone bank of chimeric plasmids containing restriction enzyme digest fragments of pLZ64 DNA was constructed in Escherichia coli K-12. One clone contained the gene coding for beta-D-phosphogalactoside galactohydrolase on a 7.9-kilobase PstI fragment cloned into the vector pBR322 in E. coli strain chi 1849. The beta-D-phosphogalactoside galactohydrolase enzyme isolated from E. coli showed no difference from that isolated from L. casei, and specific activity of beta-D-phosphogalactoside galactohydrolase was stimulated 1.8-fold in E. coli by growth in media containing beta-galactosides. A restriction map of the recombinant plasmid was compiled, and with that information, a series of subclones was constructed. From an analysis of the proteins produced by minicells prepared from transformant E. coli cells containing each of the recombinant subclone plasmids, it was found that the gene for the 56-kilodalton beta-D-phosphogalactoside galactohydrolase was transcribed from an L. casei-derived promoter. The gene for a second protein product (43 kilodaltons) was transcribed in the opposite direction, presumably under the control of a promoter in pBR322. The relationship of this second product to the lactose metabolism genes of L. casei is at present unknown.

Xylitol-mediated transient inhibition of ribitol utilization by Lactobacillus casei

The growth of Lactobacillus casei strain Cl-16 at the expense or ribitol was inhibited if the non-metabolizable substrate xylitol was included in the medium at concentrations of 6 mM or greater. At these concentrations, xylitol, did not competitively inhibit ribitol transport. The cessation of growth was caused by the intracellular accumulation of xylitol-5-phosphate, which occurred because growth on ribitol had gratuitously induced a functional xylitol-specific phosphotransferase system but not the enzymes necessary for the further metabolism of xylitol-5-phosphate. Eventually, the cells overcame the xylitol-mediated inhibition by repressing the synthesis of enzyme II of the xylitol phosphotransferase system so that xylitol-5-phosphate would no longer be accumulated within the cell.

The phosphoenolpyruvate : methyl-alpha-d-glucoside phosphotransferase system in Bacillus subtilis Marburg : kinetic studies of enzyme ii and evidence for a phosphoryl enzyme ii intermediate

The Enzyme II complex catalyzing the phosphoryl transfer from P-HPr to sugar in the inducible methyl-alpha-D-glucoside : phosphotransferase system in Bacillus subtilis acts according to a ping-pong mechanism, implying a phosphorylated Enzyme II intermediate. This result is supported by the demonstration of a specific transphosphorylation between [14C] alphaMG and glucose-6-phosphate in the presence of an induced Enzyme II preparation.

Initial characterization of hexose and hexitol phosphoenolpyruvate-dependent phosphotransferases of Staphylococcus aureus

The phosphoenolpyruvate sugar phosphotransferases of Staphylococcus aureus were surveyed biochemically to determine substrate range, inducibility and constitutivity, and requirements for soluble sugar-specific proteins. The substrate range is similar to that of the phosphotransferases of enteric bacteria, but the staphylococcal mannose and sorbitol systems are very inefficient. In addition, S. qureus has phosphotransferase activities for lactose and sucrose. The systems tested fell into two broad classes. Sugars for which there was substantial constitutive activity (fructose, mannose, sucrose, and glucose and its nonmetabolized analogues) did not require sugar-specific soluble factors for phosphorylation. Only in the case of fructose did growth in the presence of these constitutive sugars induce the corresponding phosphotransferase activity to higher levels. Kinetic experiments with each of these constitutive sugars yielded biphasic Hofstee plots; i.e., the kinetics were not characteristic of single enzymes. Preliminary experiments suggest that sucrose phosphorylation may involve the glucose and/or fructose systems. Truly inducible sugar phosphotransferase systems represent a second class; those for lactose and mannitol are the only members thus far identified. These systems are absent from uninduced cells, require soluble sugar-specific factors, and exhibit linear Hofstee plots. Sorbitol is apparently transported very poorly by intact cells but is an inducer of the mannitol system; it is phosphorylated efficiently in vitro by extracts of cells grown on either hexitol, but is taken up by intact cells at 0.1% of the mannitol rate.

Studies on the mechanism of phosphorylation and transport of beta-galactosides by the lactose phosphotransferase system of Staphylococcus aureus. Kinetic investigations using tosyl galactosides as reversible dead-end inhibitors

Tosyl galactosides, previously shown to be potent reversible dead-end inhibitors of the membrane-bound Enzyme IIlac of the lactose phosphotransferase system of Staphylococcus aureus, were used for an investigation of the kinetic mechanism of the sugar phosphorylation/transport reaction catalyzed by this enzyme: phospho-Factor IIIlac&sugar Enzyme IIlac lead to Factor IIIlac&sugar phosphate. Inhibition of Enzyme IIlac was studied in three different systems. Washed membranes, and washed membranes in the presence of 0.1% Triton X-100 were used for phosphorylation experiments, and whole cells were used for transport studies. When washed membranes were used to supply Enzyme IIlac, inhibition of phosphorylation by tosyl galactoside was linear non-competitive against both the sugar and phospho-Factor IIIlac substrates, with an apparent Ki of about 0.5 mM. This Ki decreased with increasing Factor IIIlac concentration. In the presence of 0.1% Triton X-100, the phosphorylation reaction was stimulated; under these conditions the inhibition became strictly competitive against sugar, and completely uncompetitive against phospho-Factor IIIlac. Apparently washed membranes can catalyze phosphorylation both via a reaction sequence in which sugar binds first and via one in which phospho-Factor IIIlac binds first, but in the presence of 0.1% Triton the reaction does not occur by the former sequence. The inability of bound phospho-Factor IIIlac to hinder the binding of tosyl galactosides suggests that the initial binding sites of the two substrates of Enzyme IIlac are separated by at least the distance of the tosyl moiety. Radioactive methyl 6-O-(p-toluenesulfonyl) beta-galactoside was not converted into a phosphorylated product in the reaction mixtures, i.e. it is a true dead-end inhibitor. Inhibition of beta-galactoside transport into whole cells by tosyl galactosides was competitive, with an apparent Ki of 5-10 mM, an order of magnitude higher than the Ki for inhibition of phosphorylation by membrane preparations. This result suggest that a significant level of unphosphorylated phospho-Factor IIIlac is present inside the cells, or that cellular levels of this compound are considerably lower than those used for in vitro sugar phosphorylation assays. Radioactive tosyl galactoside inhibitor was not transported into whole cells.

Conservation and transformation of energy by bacterial membranes

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