Protein H — a surface protein of Streptococcus pyogenes with separate binding sites for lgG and albumin

Inga‐Maria ‐M Frick, Per Åkesson, Jakki Cooney, Ulf Sjöbring, Karl‐Hermann ‐H Schmidt, Hideyuki Gomi, Shizuo Hattori, Chiaki Tagawa, Fumitaka Kishimoto, Lars Björck

Research output: Contribution to journalArticlepeer-review

Abstract

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 × 109M−1, which is higher than the affinity between lgG and protein H (Ka= 1.6 × 109 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.

Original languageEnglish
Pages (from-to)143-151
Number of pages9
JournalMolecular Microbiology
Volume12
Issue number1
DOIs
Publication statusPublished - Apr 1994
Externally publishedYes

Fingerprint

Dive into the research topics of 'Protein H — a surface protein of Streptococcus pyogenes with separate binding sites for lgG and albumin'. Together they form a unique fingerprint.

Cite this