A microbiologist is studying the structure and function of bacterial cell walls. In an experiment, group A streptococci are treated with chemicals to solubilize the cell wall. Various cell wall-associated proteins are subsequently extracted. Electron microscopic evaluation of a specific protein shows structural homology with mammalian tropomyosin and myosin. This protein acts as a virulence factor for certain species of the organism. Which of the following is the most likely function of this bacterial cell wall-associated protein?

Question

A microbiologist is studying the structure and function of bacterial cell walls.  In an experiment, group A streptococci are treated with chemicals to solubilize the cell wall.  Various cell wall-associated proteins are subsequently extracted.  Electron microscopic evaluation of a specific protein shows structural homology with mammalian tropomyosin and myosin.  This protein acts as a virulence factor for certain species of the organism.  Which of the following is the most likely function of this bacterial cell wall-associated protein?

Quizplus · Accepted Answer

Eductional Objective: The major virulence factor of Streptococcus pyogenes is M protein, an alpha-helical coiled-coil protein that shares structural homology with tropomyosin and myosin.  It extends from the cell wall and prevents phagocytosis, inhibits complement binding, and mediates bacterial adherence.  Antibodies against M protein form shortly after acute infection and may cross-react with epitopes on myosin, leading to rheumatic carditis.

A Microbiologist Is Studying the Structure and Function of Bacterial