Nucleotide substitutions and small-scale insertion produce size and antigenic variation in group A streptococcal M1 protein |
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| Authors: | M P Harbaugh A Podbielski S Hügl P P Cleary |
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| Institution: | Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Avenue, St. Paul, Minnesota 55108, USA.;Institute of Medical Microbiology, Technical University (RWTH), Pauwelsstrasse 30, 5100 Aachen, Germany.;Department of Microbiology, University of Minnesota, Box 196 UMHC, Mayo Building, 420 Delaware Street S.E., Minneapolis, Minnesota 55455, USA. |
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| Abstract: | The presence of M protein on the surface of group A streptococci (GAS) confers the ability of the cell to resist phagocytosis in the absence of type-specific antibodies. It undergoes antigenic variation with more than 80 different serotypes having been defined. We have sequenced the M protein gene (emm1.1) from strain CS190 and present evidence that individual nucleotide substitutions are responsible for sequence variation in the N-terminal non-repeat region of emm1.1 and these substitutions have altered antibody recognition of opsonic epitopes. The N-terminal non-repeat domains of two other closely related strains, 71-155 and 76-088, were found to have sequence identical to emm1.1 with the addition of a 21 bp insert. This study provides the first evidence that nucleotide substitutions and small insertions are responsible for size and antigenic variation in the N terminal non-repeat domain of the M protein of GAS. |
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