The primary structure of Salmonella typhimurium HPr, a phosphocarrier protein of the phosphoenolpyruvate:glycose phosphotransferase system. A correction

How phosphotransferase system-related protein phosphorylation regulates carbohydrate metabolism in bacteria

The phosphoenolpyruvate(PEP):carbohydrate phosphotransferase system (PTS) is found only in bacteria, where it catalyzes the transport and phosphorylation of numerous monosaccharides, disaccharides, amino sugars, polyols, and other sugar derivatives. To carry out its catalytic function in sugar transport and phosphorylation, the PTS uses PEP as an energy source and phosphoryl donor. The phosphoryl group of PEP is usually transferred via four distinct proteins (domains) to the transported sugar bound to the respective membrane component(s) (EIIC and EIID) of the PTS. The organization of the PTS as a four-step phosphoryl transfer system, in which all P derivatives exhibit similar energy (phosphorylation occurs at histidyl or cysteyl residues), is surprising, as a single protein (or domain) coupling energy transfer and sugar phosphorylation would be sufficient for PTS function. A possible explanation for the complexity of the PTS was provided by the discovery that the PTS also carries out numerous regulatory functions. Depending on their phosphorylation state, the four proteins (domains) forming the PTS phosphorylation cascade (EI, HPr, EIIA, and EIIB) can phosphorylate or interact with numerous non-PTS proteins and thereby regulate their activity. In addition, in certain bacteria, one of the PTS components (HPr) is phosphorylated by ATP at a seryl residue, which increases the complexity of PTS-mediated regulation. In this review, we try to summarize the known protein phosphorylation-related regulatory functions of the PTS. As we shall see, the PTS regulation network not only controls carbohydrate uptake and metabolism but also interferes with the utilization of nitrogen and phosphorus and the virulence of certain pathogens.

Genetic map of Salmonella typhimurium, edition VIII

We present edition VIII of the genetic map of Salmonella typhimurium LT2. We list a total of 1,159 genes, 1,080 of which have been located on the circular chromosome and 29 of which are on pSLT, the 90-kb plasmid usually found in LT2 lines. The remaining 50 genes are not yet mapped. The coordinate system used in this edition is neither minutes of transfer time in conjugation crosses nor units representing "phage lengths" of DNA of the transducing phage P22, as used in earlier editions, but centisomes and kilobases based on physical analysis of the lengths of DNA segments between genes. Some of these lengths have been determined by digestion of DNA by rare-cutting endonucleases and separation of fragments by pulsed-field gel electrophoresis. Other lengths have been determined by analysis of DNA sequences in GenBank. We have constructed StySeq1, which incorporates all Salmonella DNA sequence data known to us. StySeq1 comprises over 548 kb of nonredundant chromosomal genomic sequences, representing 11.4% of the chromosome, which is estimated to be just over 4,800 kb in length. Most of these sequences were assigned locations on the chromosome, in some cases by analogy with mapped Escherichia coli sequences.

Novel proteins of the phosphotransferase system encoded within the rpoN operon of Escherichia coli. Enzyme IIANtr affects growth on organic nitrogen and the conditional lethality of an erats mutant

Two rpoN-linked delta Tn10-kan insertions suppress the conditionally lethal erats allele. One truncates rpoN while the second disrupts another gene (ptsN) in the rpoN operon and does not affect classical nitrogen regulation. Neither alter expression of era indicating that suppression is post-translational. Plasmid clones of ptsN prevent suppression by either disruption mutation indicating that this gene is important for lethality caused by erats. rpoN and six neighboring genes were sequenced and compared with sequences in the database. Two of these genes encode proteins homologous to Enzyme IIAFru and HPr of the phosphoenolpyruvate:sugar phosphotransferase system. We designate these proteins IIANtr (ptsN) and NPr (npr). Purified IIANtr and NPr exchange phosphate appropriately with Enzyme I, HPr, and Enzyme IIA proteins of the phosphoenolpyruvate: sugar phosphotransferase system. Several sugars and tricarboxylic acid cycle intermediates inhibited growth of the ptsN disruption mutant on medium containing an amino acid or nucleoside base as a combined source of nitrogen, carbon, and energy. This growth inhibition was relieved by supplying the ptsN gene or ammonium salts but was not aleviated by altering levels of exogenously supplied cAMP. These results support our previous proposal of a novel mechanism linking carbon and nitrogen assimilation and relates IIANtr to the unknown process regulated by the essential GTPase Era.

Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria

Numerous gram-negative and gram-positive bacteria take up carbohydrates through the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS). This system transports and phosphorylates carbohydrates at the expense of PEP and is the subject of this review. The PTS consists of two general proteins, enzyme I and HPr, and a number of carbohydrate-specific enzymes, the enzymes II. PTS proteins are phosphoproteins in which the phospho group is attached to either a histidine residue or, in a number of cases, a cysteine residue. After phosphorylation of enzyme I by PEP, the phospho group is transferred to HPr. The enzymes II are required for the transport of the carbohydrates across the membrane and the transfer of the phospho group from phospho-HPr to the carbohydrates. Biochemical, structural, and molecular genetic studies have shown that the various enzymes II have the same basic structure. Each enzyme II consists of domains for specific functions, e.g., binding of the carbohydrate or phosphorylation. Each enzyme II complex can consist of one to four different polypeptides. The enzymes II can be placed into at least four classes on the basis of sequence similarity. The genetics of the PTS is complex, and the expression of PTS proteins is intricately regulated because of the central roles of these proteins in nutrient acquisition. In addition to classical induction-repression mechanisms involving repressor and activator proteins, other types of regulation, such as antitermination, have been observed in some PTSs. Apart from their role in carbohydrate transport, PTS proteins are involved in chemotaxis toward PTS carbohydrates. Furthermore, the IIAGlc protein, part of the glucose-specific PTS, is a central regulatory protein which in its nonphosphorylated form can bind to and inhibit several non-PTS uptake systems and thus prevent entry of inducers. In its phosphorylated form, P-IIAGlc is involved in the activation of adenylate cyclase and thus in the regulation of gene expression. By sensing the presence of PTS carbohydrates in the medium and adjusting the phosphorylation state of IIAGlc, cells can adapt quickly to changing conditions in the environment. In gram-positive bacteria, it has been demonstrated that HPr can be phosphorylated by ATP on a serine residue and this modification may perform a regulatory function.

Sequence analyses and evolutionary relationships among the energy-coupling proteins Enzyme I and HPr of the bacterial phosphoenolpyruvate: sugar phosphotransferase system

We have previously reported the overexpression, purification, and biochemical properties of the Bacillus subtilis Enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system (PTS) (Reizer, J., et al., 1992, J. Biol. Chem. 267, 9158-9169). We now report the sequencing of the ptsI gene of B. subtilis encoding Enzyme I (570 amino acids and 63,076 Da). Putative transcriptional regulatory signals are identified, and the pts operon is shown to be subject to carbon source-dependent regulation. Multiple alignments of the B. subtilis Enzyme I with (1) six other sequenced Enzymes I of the PTS from various bacterial species, (2) phosphoenolpyruvate synthase of Escherichia coli, and (3) bacterial and plant pyruvate: phosphate dikinases (PPDKs) revealed regions of sequence similarity as well as divergence. Statistical analyses revealed that these three types of proteins comprise a homologous family, and the phylogenetic tree of the 11 sequenced protein members of this family was constructed. This tree was compared with that of the 12 sequence HPr proteins or protein domains. Antibodies raised against the B. subtilis and E. coli Enzymes I exhibited immunological cross-reactivity with each other as well as with PPDK of Bacteroides symbiosus, providing support for the evolutionary relationships of these proteins suggested from the sequence comparisons. Putative flexible linkers tethering the N-terminal and the C-terminal domains of protein members of the Enzyme I family were identified, and their potential significance with regard to Enzyme I function is discussed. The codon choice pattern of the B. subtilis and E. coli ptsI and ptsH genes was found to exhibit a bias toward optimal codons in these organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of phosphorylation of HPr, a phosphocarrier protein of the phosphotransferase system, in the regulation of carbon metabolism in gram-positive bacteria

HPr of the Gram-positive bacterial phosphotransferase system (PTS) can be phosphorylated by an ATP-dependent protein kinase on a serine residue or by PEP-dependent Enzyme 1 on a histidyl residue. Both phosphorylation events appear to influence the metabolism of non-PTS carbon sources. Catabolite repression of the gluconate (gnt) operon of B. subtilis appears to be regulated by the former phosphorylation event, while glycerol kinase appears to be regulated by the latter phosphorylation reaction. The extent of our understanding of these processes will be described.

Identification and characterization of two Alcaligenes eutrophus gene loci relevant to the poly(beta-hydroxybutyric acid)-leaky phenotype which exhibit homology to ptsH and ptsI of Escherichia coli

From genomic libraries of Alcaligenes eutrophus H16 in lambda L47 and in pVK100, we cloned DNA fragments which restored the wild-type phenotype to poly(beta-hydroxybutyric acid) (PHB)-leaky mutants derived from strains H16 and JMP222. The nucleotide sequence analysis of a 4.5-kb region of one of these fragments revealed two adjacent open reading frames (ORF) which are relevant for the expression of the PHB-leaky phenotype. The 1,799-bp ORF1 represented a gene which was referred to as phbI. The amino acid sequence of the putative protein I (Mr, 65,167), which was deduced from phbI, exhibited 38.9% identity with the primary structure of enzyme I of the Escherichia coli phosphoenolpyruvate:carbohydrate phosphotransferase system (PEP-PTS). The upstream 579-bp ORF2 was separated by 50 bp from ORF1. It included the 270-bp phbH gene which encoded protein H (Mr, 9,469). This protein exhibited 34.9% identity to the HPr protein of the E. coli PEP-PTS. Insertions of Tn5 in different PHB-leaky mutants were mapped at eight different positions in phbI and at one position in phbH. Mutants defective in phbH or phbI exhibited no pleiotropic effects and were not altered with respect to the utilization of fructose. However, PHB was degraded at a higher rate in the stationary growth phase. The functions of these HPr- and enzyme I-like proteins in the metabolism of PHB are still unknown. Evidence for the involvement of these proteins in regulation of the metabolism of intracellular PHB was obtained, and a hypothetical model is proposed.

Identification of a gene encoding an HPr-like protein in Aspergillus fumigatus

The gene encoding a histidine-containing protein (HPr)-like protein was identified in a cDNA library of Aspergillus fumigatus. The predicted amino acid sequence of the fungal HPr showed greater homology with HPr from Gram-positive bacteria than from Gram-negative bacteria. Since other components of the phosphoenolpyruvate: carbohydrate phosphotransferase system have not been identified in eukaryotes, this raises the question of what regulatory function the HPr-like protein might have evolved in this fungus.

Partial nucleotide sequence of the pts operon in Salmonella typhimurium: comparative analyses in five bacterial genera

The nucleotide sequence of a Salmonella typhimurium DNA segment of 549 base pairs which encompasses the operator-promoter of the pts operon, the entirety of the ptsH gene, encoding HPr of the phosphotransferase system (PTS), the first 29 nucleotides of the ptsI gene, encoding Enzyme I of the PTS, and the intercistronic region between the ptsH and ptsI genes was determined and compared with the corresponding sequence from Escherichia coli (De Reuse et al., 1985). The two sequences showed 91% overall identity, with some regions showing sequence conservation and others exhibiting relative divergence. Two open reading frames were identified in both species: one encoded HPr on the 'sense' strand (255 nucleotides; 12 nucleotide differences, no amino acid differences); the other, on the anti-sense strand, consisted of 291 nucleotides (13 nucleotide differences, 13 amino acid differences). While HPr bears a net negative charge, the putative protein encoded by the open reading frame on the anti-sense strand is strongly basic. Computer analyses of HPr proteins from five different bacterial genera revealed four regions which show strong sequence identity and therefore are presumed to be critical for maintenance of biological activity. Two of these regions were specific to Gram-positive bacteria. Proposed functions for each of these regions are discussed. Relative evolutionary distances between the HPr proteins were also computed.

DNA sequences of the cysK regions of Salmonella typhimurium and Escherichia coli and linkage of the cysK regions to ptsH

Nucleotide sequences of the cysK regions of Salmonella typhimurium and Escherichia coli have been determined. A total of 3,812 and 2,595 nucleotides were sequenced from S. typhimurium and E. coli, respectively. Open reading frames of 323 codons were found in both species and were identified as those of cysK by comparison of deduced amino acid sequences with amino- and carboxyl-terminal amino acid analyses of the S. typhimurium cysK gene product O-acetylserine (thiol)-lyase A. The two cysK DNA sequences were 85% identical, and the deduced amino acid sequences were 96% identical. The major transcription initiation sites for cysK were found to be virtually identical in the two organisms, by using primer extension and S1 nuclease protection techniques. The -35 region corresponding to the major transcription start site was TTCCCC in S. typhimurium and TTCCGC in E. coli. The deviation of these sequences from the consensus sequence TTGACA may reflect the fact that cysK is subject to positive control and requires the cysB regulatory protein for expression. Sequences downstream of cysK were found to include ptsH and a portion of ptsI, thus establishing the exact relationship of cysK with these two genes. A 290-codon open reading frame, which may represent the cysZ gene, was identified upstream of cysK.

The phosphoenolpyruvate:sugar phosphotransferase system in gram-positive bacteria: properties, mechanism, and regulation

This review consists of three major sections. The first and largest section reviews the protein constituents and known properties of the phosphotransferase systems present in well-studied Gram-positive bacteria. These bacteria include species of the following genera: (1) Staphylococcus, (2) Streptococcus, (3) Bacillus, (4) Lactobacillus, (5) Clostridium, (6) Arthrobacter, and (7) Brochothrix. The properties of the different systems are compared. The second major section deals with the regulation of carbohydrate uptake. There are four parts: (1) inhibition by intracellular sugar phosphates in Staphylococcus aureus, (2) PTS-mediated regulation of glycerol uptake in Bacillus subtilis, (3) competition for phospho-HPr in Streptococcus mutans, and (4) the possible involvement of protein kinases in the regulation of sugar uptake via the phosphotransferase system. The third section deals with the phenomenon of inducer expulsion. The first part is concerned with the physiological characterization of the phenomenon; then the consequences of unregulated uptake and expulsion, a futile cycle of energy expenditure, are considered. Finally, the biochemistry of the protein kinase and the protein phosphate phosphatase system, which appears to regulate sugar transport via the phosphotransferase system, is defined. The review, therefore, concentrates on the phosphotransferase system, its functions in carbohydrate transport and phosphorylation, the mechanisms of its regulation, and the mechanism by which it participates in the regulation of other physiological processes in the bacterial cell.

Characterization of mutant histidine-containing proteins of the phosphoenolpyruvate:sugar phosphotransferase system of Escherichia coli and Salmonella typhimurium

Histidine-containing phosphocarrier protein (HPr) is common to all of the phosphoenolpyruvate:sugar phosphotransferase systems (PTS) in Escherichia coli and Salmonella typhimurium, except the fructose-specific PTS. Strains which lack HPr activity (ptsH) have been characterized in the past, and it has proved difficult to delineate between tight and leaky mutants. In this study four different parameters of ptsH strains were measured: in vitro sugar phosphorylation activity of the mutant HPr; detection of 32P-labeled P-HPr; ability of monoclonal antibodies to bind mutant HPr; and sensitivity of ptsH strains to fosfomycin. Tight ptsH strains could be defined; they were fosfomycin resistant and produced no HPr protein or completely inactive mutant HPr. All leaky ptsH strains were fosfomycin sensitive, usually produced normal amounts of mutant HPr protein, and had low but measurable activity, and HPr was detectable as a phosphoprotein. This indicates that the regulatory functions of the PTS require a very low level of HPr activity (about 1%). The antibodies used to detect mutant HPr in crude extracts were two monoclonal immunoglobulin G antibodies Jel42 and Jel44. Both antibodies, which have different pIs, inhibited PTS sugar phosphorylation assays, but the antibody-HPr complex could still be phosphorylated by enzyme I. Preliminary evidence suggests that the antibodies bind to two different epitopes which are in part located in a beta-sheet structure.

Streptococcal phosphoenolpyruvate-sugar phosphotransferase system: amino acid sequence and site of ATP-dependent phosphorylation of HPr

The amino acid sequence of histidine-containing protein (HPr) from Streptococcus faecalis has been determined by direct Edman degradation of intact HPr and by amino acid sequence analysis of tryptic peptides, V8 proteolytic peptides, thermolytic peptides, and cyanogen bromide cleavage products. HPr from S. faecalis was found to contain 89 amino acid residues, corresponding to a molecular weight of 9438. The amino acid sequence of HPr from S. faecalis shows extended homology to the primary structure of HPr proteins from other bacteria. Besides the phosphoenolpyruvate-dependent phosphorylation of a histidyl residue in HPr, catalyzed by enzyme I of the bacterial phosphotransferase system, HPr was also found to be phosphorylated at a seryl residue in an ATP-dependent protein kinase catalyzed reaction [Deutscher, J., & Saier, M. H., Jr. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 6790-6794]. The site of ATP-dependent phosphorylation in HPr of S. faecalis has now been determined. [32P]P-Ser-HPr was digested with three different proteases, and in each case, a single labeled peptide was isolated. Following digestion with subtilisin, we obtained a peptide with the sequence -(P)Ser-Ile-Met-. Using chymotrypsin, we isolated a peptide with the sequence -Ser-Val-Asn-Leu-Lys-(P)Ser-Ile-Met-Gly-Val-Met-. The longest labeled peptide was obtained with V8 staphylococcal protease. According to amino acid analysis, this peptide contained 36 out of the 89 amino acid residues of HPr. The following sequence of 12 amino acid residues of the V8 peptide was determined: -Tyr-Lys-Gly-Lys-Ser-Val-Asn-Leu-Lys-(P)Ser-Ile-Met-.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system has two sites of phosphorylation per dimer

Enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system of Escherichia coli has been reported to contain one phosphorylation site per dimer and thus operates by either a half of the sites or a flip-flop mechanism [Misset, O., & Robillard, G. T. (1982) Biochemistry 21, 3136-3142; Hoving, T., ten Hoeve-Duurkens, R., & Robillard, G. T. (1984) Biochemistry 23, 4335-4340]. In this paper, the determination of two phosphorylation sites per dimer of enzyme I was made by using a number of different methods. In some experiments, less than two sites per dimer were found, but a concomitant loss in enzyme I activity was also found. The phosphorylated residue in enzyme I was shown to have the properties expected for a N3-phosphohistidinyl residue.

Phosphoenolpyruvate-sugar phosphotransferase transport system of Streptococcus mutans: purification of HPr and enzyme I and determination of their intracellular concentrations by rocket immunoelectrophoresis

Enzyme I and HPr, the general proteins of the phosphoenolpyruvate-sugar phosphotransferase system, play a pivotal role in the control of sugar utilization in gram-negative and gram-positive bacteria. To determine whether growth conditions could modify the rate of biosynthesis of these proteins in Streptococcus mutans, we first purified to homogeneity enzyme I and HPr from S. mutans ATCC 27352. Using specific antibodies obtained against these proteins, we determined by rocket electrophoresis the intracellular levels of enzyme I and HPr in cells of S. mutans 27352 grown under various batch culture conditions and in a number of glucose-grown cells of other strains of S. mutans. HPr was purified by the procedure reported by Gauthier et al. (L. Gauthier, D. Mayrand, and C. Vadeboncoeur, J. Bacteriol. 160:755-763, 1984) and displayed a single band with a molecular weight of 6,650 when analyzed by sodium dodecyl sulfate-urea gel electrophoresis. Enzyme I was purified by DEAE-cellulose chromatography, affinity chromatography on an anti-Streptococcus salivarius column, and preparative electrophoresis. The protein migrated as a single band in native and denaturating gel electrophoresis. The subunit molecular weight of enzyme I determined by electrophoresis under denaturating conditions was 68,000. In gel filtration chromatography at 4 degrees C, the enzyme migrated as a 135,000- to 160,000-molecular-weight species, suggesting that enzyme I is a dimer. In double immunodiffusion experiments, antibodies against HPr reacted with several oral streptococci, Streptococcus lactis, Streptococcus faecium, and Lactobacillus casei, but not with Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. Antibodies against enzyme I of S. mutans 27352 cross-reacted with enzyme I from all the other oral streptococci tested. No cross-reaction was observed with other gram-positive and gram-negative bacteria. The levels of enzyme I and HPr determined by rocket electrophoresis in S. mutans 27352 varied at the most by twofold, depending on the growth conditions. Glucose-grown cells of other S. mutans strains contained levels of enzyme I and HPr which were similar to those found in S. mutans 27352.