True about protein A of staph aureus:

Ans. is 'b' i.e., Binds to Fc part of IgG(Ref: Ananthanarayan, 9th/e, p. 197, 198)* Protein A is a cell wall component of S aureus strains and is a bacterial surface protein called as microbial surface components recognizing adhesive matrix molecules (MSCRAMMs).Bacterial attachment to host cells is mediated by MSCRAMMs, and these are important virulence factors.Protein A of Staph aureus binds to Fc terminal of IgG (IgG 1, 2 and 4 but not IgG 3) and prevents opsono- phagocytosis by PMNs.* Protein A has become an important reagent in immunology and diagnostic laboratory technology; for example, protein A with attached IgG molecules directed against a specific bacterial antigen agglutinates bacteria that have that antigen ("conglutination").