Hypoxanthine-guanine phosphoribosyltransferase from beef brain: A trimer

Hypoxanthine-guanine phosphoribosyl isolated from beef brain was reacted with cross-linking reagents in order to establish the number of subunits that constitute the native protein. The results obtained from experiments with dimethyl-suberimidate and gluteraldehyde in the absence and in the presence of substrates all indicate that the native structure is a trimer.