Question

Why are many opsonins multimeric?

A. Because they are all derived from the same proto-opsonin
B. Because they bind repeating structures on pathogen surfaces
C. So that they can be regulated allosterically
D. Because they have to crosslink receptors on phagocytes in order for phagocytosis to occur
E. Because one subunit binds pathogen and the other has enzymatic activity

Answer 1

Opsonins are often multimeric because their multivalency allows for more efficient binding to repeating structures on pathogen surfaces, facilitating the recognition and ingestion by phagocytes.

Step-by-step explanation:

Many opsonins are multimeric because they bind to repeating structures on the surfaces of pathogens. This multivalency allows for a stronger and more efficient binding, which is critical for the opsonization process. During opsonization, molecules like IgG antibodies or complement factors coat a pathogen to facilitate its recognition and ingestion by phagocytic cells such as macrophages and neutrophils. These phagocytic cells have receptors that recognize the Fc portion of IgG molecules or the C3b fragment of complement, thereby enabling attachment before phagocytosis. Multimeric opsonins, therefore, effectively bridge pathogens to phagocytic cells, enhancing the immune response against infections.