TY - JOUR
T1 - Protein H-A novel igg binding bacterial protein
AU - Åkesson, Per
AU - Cooney, Jakki
AU - Kishimoto, Fumitaka
AU - Björck, Lars
PY - 1990/6
Y1 - 1990/6
N2 - Forty-eight group A streptococcal strains of different M types were screened for binding of human radiolabeled IgG. Three of the strains bound more than 80% of the added radioactivity and one of them, an M protein type 1 strain designated API, was selected for further analysis. Attempts were made to solubilize the IgG binding bacterial molecule, and small amounts of an IgG binding protein with a mol. wt of 40 kDa could be solubilized with mutanolysin, a muramolytic agent. The gene encoding this streptococcal protein was cloned and expressed in E. coli, and the E. coli-produced protein was purified in a single step by affinity chromatography on IgG-Sepharose. When tested with IgGs from different species, the molecule was found to bind human IgG almost exclusively. The N-terminal amino acid sequence was determined and showed no homology with previously isolated Ig binding proteins, and the name protein H (as in human IgG) is suggested for this novel Ig binding bacterial protein. p]Protein H showed preferential affinity for heavy chains and Fc fragments of human IgG, and did not bind Ig light chains. The affinity constant, determined by Scatchard plots, between protein H and human polyclonal IgG was 1.6 × 109. No binding was observed between protein H and IgM, IgA, IgD, or IgE. Finally, when tested against several additional proteins and human plasma, protein H only showed weak binding to α2-macroglobulin, a proteinase inhibitor.
AB - Forty-eight group A streptococcal strains of different M types were screened for binding of human radiolabeled IgG. Three of the strains bound more than 80% of the added radioactivity and one of them, an M protein type 1 strain designated API, was selected for further analysis. Attempts were made to solubilize the IgG binding bacterial molecule, and small amounts of an IgG binding protein with a mol. wt of 40 kDa could be solubilized with mutanolysin, a muramolytic agent. The gene encoding this streptococcal protein was cloned and expressed in E. coli, and the E. coli-produced protein was purified in a single step by affinity chromatography on IgG-Sepharose. When tested with IgGs from different species, the molecule was found to bind human IgG almost exclusively. The N-terminal amino acid sequence was determined and showed no homology with previously isolated Ig binding proteins, and the name protein H (as in human IgG) is suggested for this novel Ig binding bacterial protein. p]Protein H showed preferential affinity for heavy chains and Fc fragments of human IgG, and did not bind Ig light chains. The affinity constant, determined by Scatchard plots, between protein H and human polyclonal IgG was 1.6 × 109. No binding was observed between protein H and IgM, IgA, IgD, or IgE. Finally, when tested against several additional proteins and human plasma, protein H only showed weak binding to α2-macroglobulin, a proteinase inhibitor.
UR - http://www.scopus.com/inward/record.url?scp=0025372126&partnerID=8YFLogxK
U2 - 10.1016/0161-5890(90)90071-7
DO - 10.1016/0161-5890(90)90071-7
M3 - Article
C2 - 2199820
AN - SCOPUS:0025372126
SN - 0161-5890
VL - 27
SP - 523
EP - 531
JO - Molecular Immunology
JF - Molecular Immunology
IS - 6
ER -