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Category: Bacterial Pathogenesis
Genetics and Pathogenicity Factors of Group C and G Streptococci, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap16-1.gif /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap16-2.gifAbstract:
The application of recombinant DNA techniques has advanced one's understanding of group C streptococci (GCS) and group G streptococci (GGS) in diverse areas, and this chapter concentrates on the structure and function of pathogenetically relevant genes and proteins studied at the molecular level in recent years. On the basis of 16S rRNA comparative sequence analysis, GCS and GGS fall into two species groups, the pyogenic and the anginosus group; the latter is also known as “Streptococcus milleri” group. One hallmark of the gram-positive pathogens is the synthesis of specific cell wall-associated proteins that enable them to interact in various ways with proteins present in the body fluids or extracellular tissue matrix of their mammalian hosts. Such interactions may facilitate colonization, lead to molecular host mimicry, or interfere with various host defenses against invasion. The cell wall-associated proteins discussed are M and M-like proteins, immunoglobulin G (IgG)-binding proteins, fibronectin-binding proteins, and plasmin(ogen)-binding proteins. Other covered topics are cytoplasmic membrane-associated enzymes such as hyaluronan synthase and cytoplasmic membrane lipoprotein acid phosphatase, and extracellular proteins. The chapter ends with a discussion on the stringent and relaxed responses of Streptococcus dysgalactiae subsp. equisimilis.
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Schematic representation of the domain organization of protein G. S, signal sequence; E, α2-macroglobulin-binding; A and B, human serum albumin-binding; C, IgG-binding; W, cell wall-associated region; M, cell membrane-associated region. (Adapted from reference 124 )
Schematic representation of the domain organization of protein G. S, signal sequence; E, α2-macroglobulin-binding; A and B, human serum albumin-binding; C, IgG-binding; W, cell wall-associated region; M, cell membrane-associated region. (Adapted from reference 124 )
Organization of the streptokinase-M protein gene region in the S. dysgalactiae subsp. equisimilis H46A chromosome based on references 38 and 98 . Arrows represent the genes and their orientation: nrdI, ribonucleotide reductase; mgc, multigene regulator of GCS; emm, M protein; cpdB, 2′,3′-cyclic nucleotide 2′-phosphodiesterase; rel, bifunctional (p)ppGppase and (p)ppGpp synthetase; dtd, D-tyrosyl-tRNATyr deacylase; skc, streptokinase; lrp, leucine-rich protein of unknown function; abc, ATP-binding cassette transporter; dexB, α-glucosidase.
Organization of the streptokinase-M protein gene region in the S. dysgalactiae subsp. equisimilis H46A chromosome based on references 38 and 98 . Arrows represent the genes and their orientation: nrdI, ribonucleotide reductase; mgc, multigene regulator of GCS; emm, M protein; cpdB, 2′,3′-cyclic nucleotide 2′-phosphodiesterase; rel, bifunctional (p)ppGppase and (p)ppGpp synthetase; dtd, D-tyrosyl-tRNATyr deacylase; skc, streptokinase; lrp, leucine-rich protein of unknown function; abc, ATP-binding cassette transporter; dexB, α-glucosidase.
Sequence comparison of E. coli and S. pyogenes σ factors ( 5 ) between region 2.4 and the start of region 3. Identical and similar amino acids are marked by asterisks and dots, respectively. The residues identified in E. coli as contacting the TG extension of the −10 promoter hexamer are indicated by open boxes.
Sequence comparison of E. coli and S. pyogenes σ factors ( 5 ) between region 2.4 and the start of region 3. Identical and similar amino acids are marked by asterisks and dots, respectively. The residues identified in E. coli as contacting the TG extension of the −10 promoter hexamer are indicated by open boxes.
Bootstrapped (1,000 trials) neighbor-joining phylogenetic tree of the FasA-BlpRComE family of streptococcal response regulators graphed by the MEGA2 software ( 72 ) based on ClustalX multiple alignment (http://www.ncbi.nlm.nih.gov). Species abbreviations and sources of the proteins are as follows: Sag1, S. agalactiae, AF390107; San1, S. anginosus, AJ000864; Sau1, identical to AgrA from Staphylococcus aureus, AY082629; Sdy1, S. dysgalactiae subsp. equisimilis, AY075107; Seq1, Seq2, Seq3, S. equi subsp. equi, http://www.sanger.ac.uk/Projects/S_equi; Sgo1, S. gordonii, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Sgo2, X98109; Sin1, S. infantis, AF498313; Smi1, S. mitis, AJ000871; Smi2, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Smu1, S. mutans, AE015016; Sor1, S. oralis, AJ240794; Spn1, S. pneumoniae, AJ278302; Spn2, AJ240793; Spy1, S. pyogenes, AE009971; Spy2, AE009991; Sso1, Sso2, S. sobrinus, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Ssu1, S. suis, AY125957; Sub1, S. uberis, http://www.sanger.ac.uk/Projects/S_uberis; Szo1, Szo2, S. equi subsp. zooepidemicus, http://www.sanger.ac.uk/Projects/S_zooepidemicus. When sets of sequences >90% identical were identified in the same species, only one sequence was included to avoid analysis of duplicate sequences. For taxonomic reasons, the exception was S. equi, for which both subspecies are included in spite of Seq1 and Szo1 on one hand, and Seq2 and Szo2 on the other, being >90% identical. Bootstrap confidence estimates (%) are given next to the tree nodes: groups found in >95% of trials are considered well supported, those found in >50% are considered suggestive.
Bootstrapped (1,000 trials) neighbor-joining phylogenetic tree of the FasA-BlpRComE family of streptococcal response regulators graphed by the MEGA2 software ( 72 ) based on ClustalX multiple alignment (http://www.ncbi.nlm.nih.gov). Species abbreviations and sources of the proteins are as follows: Sag1, S. agalactiae, AF390107; San1, S. anginosus, AJ000864; Sau1, identical to AgrA from Staphylococcus aureus, AY082629; Sdy1, S. dysgalactiae subsp. equisimilis, AY075107; Seq1, Seq2, Seq3, S. equi subsp. equi, http://www.sanger.ac.uk/Projects/S_equi; Sgo1, S. gordonii, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Sgo2, X98109; Sin1, S. infantis, AF498313; Smi1, S. mitis, AJ000871; Smi2, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Smu1, S. mutans, AE015016; Sor1, S. oralis, AJ240794; Spn1, S. pneumoniae, AJ278302; Spn2, AJ240793; Spy1, S. pyogenes, AE009971; Spy2, AE009991; Sso1, Sso2, S. sobrinus, http://www.tigr.org/tdb/mdb/mdbinprogress.html; Ssu1, S. suis, AY125957; Sub1, S. uberis, http://www.sanger.ac.uk/Projects/S_uberis; Szo1, Szo2, S. equi subsp. zooepidemicus, http://www.sanger.ac.uk/Projects/S_zooepidemicus. When sets of sequences >90% identical were identified in the same species, only one sequence was included to avoid analysis of duplicate sequences. For taxonomic reasons, the exception was S. equi, for which both subspecies are included in spite of Seq1 and Szo1 on one hand, and Seq2 and Szo2 on the other, being >90% identical. Bootstrap confidence estimates (%) are given next to the tree nodes: groups found in >95% of trials are considered well supported, those found in >50% are considered suggestive.
(See the separate color insert for the color version of this illustration.) Structure of Rel Seq 1-385. (A) ppGpp Hydrolase-OFF/synthetase-ON conformation, in complex with Mn2+ (blue sphere) and GDP (stick rendering). The hydrolase domain is highlighted in green α-helices and blue β-strands, the synthetase domain is in yellow α -helices and orange β -strands, and the central 3-helix bundle is in red. Part of the substrate-binding cleft comprising the hydrolase site (downregulated) is disordered (red arrow). The small synthetase/hydrolase interdomain contact interface involved in signal transmission is labeled with a red star. (B) Hydrolase-ON/synthetase-OFF conformation, in complex with Mn2+, ppG′:3′p (which locks the enzyme in the hydrolase-ON/synthetase-OFF conformation) and GDP. The coloring and rendering schemes are the same as for (A). The disordered synthetase site (down-regulated) is illustrated as dashed lines with a red arrow. (C) Primary and secondary structure of Rel Seq 1-385. Secondary structure is color-coded according to (A) and (B). Unique secondary structure assignments for (A) are placed immediately below the corresponding assignments for (B). Residues absolutely conserved throughout the mono- and bifunctional RelA and SpoT homologs are underlaid with blue boxes. Residues conserved in SpoT and the bifunctional enzymes but mutated in the hydrolase-incompetent RelA homologs are underlaid with red boxes. Upright and inverted black triangles above the sequence indicate residues which, when substituted experimentally by missense mutations, lead to defective hydrolase and synthetase activities, respectively. (Reproduced from reference 51 , with permission.)
(See the separate color insert for the color version of this illustration.) Structure of Rel Seq 1-385. (A) ppGpp Hydrolase-OFF/synthetase-ON conformation, in complex with Mn2+ (blue sphere) and GDP (stick rendering). The hydrolase domain is highlighted in green α-helices and blue β-strands, the synthetase domain is in yellow α -helices and orange β -strands, and the central 3-helix bundle is in red. Part of the substrate-binding cleft comprising the hydrolase site (downregulated) is disordered (red arrow). The small synthetase/hydrolase interdomain contact interface involved in signal transmission is labeled with a red star. (B) Hydrolase-ON/synthetase-OFF conformation, in complex with Mn2+, ppG′:3′p (which locks the enzyme in the hydrolase-ON/synthetase-OFF conformation) and GDP. The coloring and rendering schemes are the same as for (A). The disordered synthetase site (down-regulated) is illustrated as dashed lines with a red arrow. (C) Primary and secondary structure of Rel Seq 1-385. Secondary structure is color-coded according to (A) and (B). Unique secondary structure assignments for (A) are placed immediately below the corresponding assignments for (B). Residues absolutely conserved throughout the mono- and bifunctional RelA and SpoT homologs are underlaid with blue boxes. Residues conserved in SpoT and the bifunctional enzymes but mutated in the hydrolase-incompetent RelA homologs are underlaid with red boxes. Upright and inverted black triangles above the sequence indicate residues which, when substituted experimentally by missense mutations, lead to defective hydrolase and synthetase activities, respectively. (Reproduced from reference 51 , with permission.)
Classification of GCS and GGS a
a Adapted from references cited in the text.
b Uncommonly, this subspecies may also comprise serogroup A and L strains and may also be found in animals.
Classification of GCS and GGS a
a Adapted from references cited in the text.
b Uncommonly, this subspecies may also comprise serogroup A and L strains and may also be found in animals.