title: Crosslinking of actin filaments and inhibition of actomyosin subfragment-1 ATPase activity by streptococcal M6 protein.
abstract: M proteins are antiphagocytic molecules on the surface of group A streptococci having physical characteristics similar to those of mammalian tropomyosin. Both are alpha-helical coiled-coil fibrous structures with a similar seven-residue periodicity of nonpolar and charged amino acids. To determine if M protein is functionally similar to tropomyosin we studied the interaction of M protein with F-actin. At low ionic strength, M protein binds to actin weakly with a stoichiometry different from that of tropomyosin. M protein does not compete with tropomyosin for the binding to actin, indicating that it is functionally different from tropomyosin. M protein does compete with myosin subfragment-1 for binding to actin and induces the formation of bundles of actin filaments. The formation of actin aggregates is associated with a sharp reduction in the rate of ATP hydrolysis by subfragment-1. Intact streptococci having M protein on their surface are shown to bind to actin.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D014335:Tropomyosin / Q000378:metabolism
chemical_list: D000199:Actins; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D014335:Tropomyosin; C014689:streptococcal M protein; D000251:Adenosine Triphosphatases; D009218:Myosins