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Protein H — a surface protein of Streptococcus pyogenes with separate binding sites for lgG and albumin
Author(s) -
Frick IngaMaria,
Åkesson Per,
Cooney Jakki,
Sjöbring Ulf,
Schmidt KarlHermann,
Gomi Hideyuki,
Hattori Shizuo,
Tagawa Chiaki,
Kishimoto Fumitaka,
Björck Lars
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb01003.x
Subject(s) - protein g , streptococcus pyogenes , biology , albumin , protein a/g , binding protein , microbiology and biotechnology , biochemistry , binding site , protein a , plasma protein binding , serum albumin , peptide sequence , antibody , recombinant dna , bacteria , gene , fusion protein , staphylococcus aureus , genetics
Summary Protein H, a molecule expressed at the surface of some strains of Streptococcus pyogenes , has affinity for the constant (lgGFc) region of immunoglobulin (lg) G. In absorption experiments with human plasma, protein H–sepharose could absorb not only lgG but also albumin from plasma. The affinity constant for the reaction between albumin and protein H was 7.8 × 10 9 M −1 , which is higher than the affinity between lgG and protein H (K a = 1.6 × 10 9 M −1 ). Fragments of protein H were generated with deletion plasmids and polymerase chain reaction (PCR) technology. Using these fragments in various protein–protein interaction assays, the binding of albumin was mapped to three repeats (C1–C3) in the C ‐terminal half of protein H. On the albumin molecule, the binding site for protein H was found to overlap the site for protein G, another albumin‐ and lgGFc‐binding bacterial surface protein. Aiso lgGFc‐binding could be mapped with the protein H fragments and the region was found N ‐terminally of the C repeats. A synthetic peptide (25 amino acid residues long) based on a sequence in this region was shown to inhibit the binding of protein H to immobilized lgG or lgGFc. This sequence was not found in previously described lgGFc‐binding proteins. However, two other cell surface proteins of S. pyogenes exhibited highly homologous regions. The results identify lgGFc‐ and albumin binding regions of protein H and further define and emphasize the convergent evolution among bacterial surface proteins interacting with human plasma proteins.