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Infect. Immun., Jan 1998, 259-265, Vol 66, No. 1
MW Stinson, R McLaughlin, SH Choi, ZE Juarez and J Barnard
In addition to its role in the nucleoid, the histone-like protein (HlpA) of
Streptococcus pyogenes is believed to act as a fortuitous virulence factor
in delayed sequelae by binding to heparan sulfate- proteoglycans in the
extracellular matrix of target organs and acting as a nidus for in situ
immune complex formation. To further characterize this protein, the hlpA
genes were cloned from S. pyogenes, S. gordonii, S. mutans, and S.
sobrinus, using PCR amplification, and sequenced. The encoded HlpA protein
of S. pyogenes has 91 amino acids, a predicted molecular mass of 9,647 Da,
an isoelectric point of 9.81, and 90% to 95% sequence identity with HlpA of
several oral streptococci. The consensus sequence of streptococcal HlpA has
69% identity with the consensus sequence of the histone-like HB protein of
Bacillus species. Oral viridans group streptococci, growing in chemically
defined medium at pH 6.8, released HlpA into the milieu during stationary
phase as a result of limited cell lysis. HlpA was not released by these
bacteria when grown at pH 6.0 or below. S. pyogenes did not release HlpA
during growth in vitro; however, analyses of sera from 155 pharyngitis
patients revealed a strong correlation (P < 0.0017) between the
production of antibodies to HlpA and antibodies to streptolysin O,
indicating that the histone-like protein is released by group A
streptococci growing in vivo. Extracellular HlpA formed soluble complexes
with lipoteichoic acid in vitro and bound readily to heparan sulfate on
HEp-2 cell surfaces. These results support a potential role for HlpA in the
pathogenesis of streptococcus-induced tissue inflammation.
Copyright © 1998, American Society for Microbiology
Streptococcal histone-like protein: primary structure of hlpA and protein binding to lipoteichoic acid and epithelial cells
Department of Microbiology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 14214, USA. mstinson@ubmedb.buffalo.edu
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