CLONING AND SEQUENCE-ANALYSIS OF A PROTECTIVE M-LIKE PROTEIN GENE FROM STREPTOCOCCUS-EQUI SUBSP ZOOEPIDEMICUS

Streptococcus equi subsp, zooepidemicus, a Lancefield group C streptoc occus, is a frequently isolated opportunist pathogen from a variety of animal hosts, including the horse, Previous studies have indicated th at equine strains carry antigens with characteristics of the antiphago cytic M proteins on the Lancefield groups A and G streptococci, We hav e cloned a protective M-like protein gene (SzPW60) of an equine strain of S. equi subsp. zooepidemicus W60 and determined its sequence, This gene encodes a protein with a molecular weight of 40,123 which protec ts mice against subsp, zooepidemicus but not subsp, equi, stimulates a ntibodies which opsonize subsp, zooepidemicus but not equi, and reacts with antiserum to the protein of the parent strain, The predicted ami no acid structure shows significant homology with the carboxy termini of groups A and G M proteins but no other homology, The M-like protein , although showing an extensive region of alpha helix, lacks the A, B, and C repeats found in group A M proteins and has a shorter signal se quence. A proline-rich region upstream from the LPSTGE motif contains 20 repeats of the tetrapeptide PEPK. The presence of this repeat regio n may account for the slow migration of the M-like protein in sodium d odecyl sulfate-polyacrylamide gel electrophoresis.