A comparison of the trypsinolysis products of nine 11S globulin species

The trypsinolysis of nine different US globulin species in high ionic strength conditions has been studied in relation to changes observed in subunit composition and quaternary/tertiary structure. HPLC gel filtration and SDS-PAGE analyses provided some information that was used to postulate the method of enzyme attack and categorize these proteins into two groups. One group of IIS globulins possessed a greatly disrupted subunit structure, the acidic polypeptides being highly degraded and the hydrolysis of the basic polypeptides being initiated. The other class of globulins, however, possessed intact basic polypeptides and only slightly cleaved acidic polypeptides (M r = 33 000) after trypsinolysis. Gel filtration analysis demonstrated that both groups of globulins still possessed much of their original structure, forming a common intermediate at M r ~ 200 000.