The Relative Importance of the Capsule and the M-Antigen in Determining Colony Form of Group a Streptococci

Wilson, Armine T.

doi:10.1084/jem.109.3.257

Cited by 49 publications

(35 citation statements)

References 17 publications

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“…Other factors that have been proposed as important for virulence of group A streptococci include the hyaluronic acid capsule, which may help protect the organisms from phagocytosis (42,43), the plasminogen-activating streptokinases, which may aid in dissemination of the streptococci in tissue (21), the immunoglobulin G Fc receptor protein (37), which may sequester opsonic immunoglobulin G antibodies, the C5a peptidase that can prevent polymorphonuclear leu-* Corresponding author.…”

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confidence: 99%

Mry, a trans-acting positive regulator of the M protein gene of Streptococcus pyogenes with similarity to the receptor proteins of two-component regulatory systems

1991

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In the Streptococcus pyogenes M6 strain D471, an insertion of the conjugative transposon Tn916 into a region 2 kb upstream of the promoter of emm6 (the structural gene for the M protein) rendered the strain M negative (M. G. Caparon and J. R. Scott, Proc. Natl. Acad. Sci. USA 84:8677-8681, 1987). In the present work, we show that this insertion mutation, mry-1, is 244 bp upstream of an open reading frame encoding a protein we call Mry. This protein is visible on a gel after transcription and translation in vitro. We have developed a technique for complementation analysis in S. pyogenes and have used it to show that the wild-type mry gene is dominant to two mutant alleles. This dominance indicates that Mry acts in trans as a positive regulator of the emm6 gene. The translated DNA sequence of mry has two regions of similarity to the motif common to the receptor protein of two-component regulatory systems. In addition, the N terminus of Mry has two regions resembling a helix-turn-helix motif. Mry does not appear to be a global regulator of virulence determinants in the group A streptococcus because there is no effect of the miy-1 mutation on production of the hyaluronic acid capsule or streptokinase.

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Mry, a trans-acting positive regulator of the M protein gene of Streptococcus pyogenes with similarity to the receptor proteins of two-component regulatory systems

1991

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“…The M-phase-locked strain, A7, which harbors a deletion in virR (Fig. 1 (17) and hyaluronic acid biosynthesis (25), to the phase switch (Fig. 5).…”

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confidence: 99%

“…The avoidance of human immunological defenses by group A streptococci is dependent on the following surface components: a diffuse hyaluronic capsule which mimics the ground substance of animal tissues (25); immunoglobulin G Fc receptors, which may disrupt recognition by antibodies (6b); a C5a peptidase which destroys chemotactic signals (23); and M protein, which interferes with the deposition of C3b opsonin to prevent phagocytic uptake (8,9). M protein, thought to be the key determinant of virulence, has been the subject of intensive investigation.…”

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Coregulation of type 12 M protein and streptococcal C5a peptidase genes in group A streptococci: evidence for a virulence regulon controlled by the virR locus

et al. 1990

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Group A streptococci express at least two surface-associated virulence factors, the antiphagocytic M protein and the antichemotactic streptococcal C5a peptidase (SCP). Preliminary evidence suggested that the biosynthesis of these two proteins is coordinately controlled and subject to simultaneous phase variation. To explore this possibility further, a series of phase-switching and phase-locked M-variants were assayed for SCP by enzyme-linked immunosorbent assay inhibition and for SCP-specific mRNA by dot blot hybridization. All Mcultures produced diminished amounts of SCP antigen and specific mRNA, whereas revertants produced quantities equivalent to those of the wild-type M' culture. A phase-locked strain that harbors a deletion in a region upstream of the M12 and SCP genes, termed the virR locus, failed to produce SCP antigen or SCP-specific transcripts. The SCP-specific transcript produced by M' bacteria was shown by Northern (RNA) blot hybridization to be 4 kilobases in size, distinguishing it from the transcript which encodes M protein. These data demonstrate that phase switching of both SCP and M12 proteins is at the transcriptional level and that expression is under the control of the upstream virR locus. We propose that the genetic determinants of these proteins and of colony morphology comprise a virulence regulon.The survival and multiplication of bacterial pathogens in a susceptible host depend on their abilities to acquire appropriate nutrients, interact with tissue receptors, and resist host defenses. A recent review (10) noted that the expression of multiple virulence determinants by gram-negative pathogens is a finely tuned process which is responsive to environmental changes and the general physiological state of the bacterial cell. It is now apparent that these virulence genes are globally controlled by a master gene which couples external stimuli to response pathways (10).The avoidance of human immunological defenses by group A streptococci is dependent on the following surface components: a diffuse hyaluronic capsule which mimics the ground substance of animal tissues (25); immunoglobulin G Fc receptors, which may disrupt recognition by antibodies (6b); a C5a peptidase which destroys chemotactic signals (23); and M protein, which interferes with the deposition of C3b opsonin to prevent phagocytic uptake (8, 9). M protein, thought to be the key determinant of virulence, has been the subject of intensive investigation. This dimeric coiled-coil molecule protrudes from the cell wall, where it both blocks the deposition of C3b opsonin and limits the interaction of bound C3b with receptors on polymorphonuclear leukocytes (8, 9). As a result, M+ streptococci are resistant to phagocytosis in the absence of type-specific M protein antibody and complement.Group A streptococcal cultures have long been recognized as genetically unstable (6,17,20). The expression of M protein on their surfaces, colony morphology, and virulence were reported to vary dramatically both in laboratory cultures (6, 17) and in st...

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“…In gonococci, opacity correlates with both specific outer membrane proteins (Opa or protein II) (25,26) and lipooligosaccharide phenotype (27). Opacity in group A streptococci was associated with the expression of M type 12 protein (22) in one study but not in others (15,28,33). Light and electron microscopic studies revealed that opaque streptococci form elongated chains (15,28,33).…”

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“…Opacity in group A streptococci was associated with the expression of M type 12 protein (22) in one study but not in others (15,28,33). Light and electron microscopic studies revealed that opaque streptococci form elongated chains (15,28,33). Virulent H. influenzae organisms are opaque, are encapsulated, and can phase shift to the nonopaque, unencapsulated phenotype (13,30).…”

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Group B streptococcal opacity variants

et al. 1992

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The Relative Importance of the Capsule and the M-Antigen in Determining Colony Form of Group a Streptococci

Cited by 49 publications

References 17 publications

Mry, a trans-acting positive regulator of the M protein gene of Streptococcus pyogenes with similarity to the receptor proteins of two-component regulatory systems

Mry, a trans-acting positive regulator of the M protein gene of Streptococcus pyogenes with similarity to the receptor proteins of two-component regulatory systems

Coregulation of type 12 M protein and streptococcal C5a peptidase genes in group A streptococci: evidence for a virulence regulon controlled by the virR locus

Group B streptococcal opacity variants

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