Order of stability for proteolysis sites of a bacterial collagen-like protein

When compared with collagens isolated from animal sources, collagens and collagen-like (CL) proteins from non-animal sources are non-immunogenic and thus promising as biomedical materials. Recently, a CL protein, V-CL, was identified from a bacterial source, Streptococcus pyogenes. In this study, an acid-precipitation method was used to isolate V-CL in one purification step. Circular dichroism spectroscopy was used to examine the triple-helix structure of V-CL. The trypsin proteolysis events of V-CL were characterized using gel electrophoresis and mass spectrometry. The proteolysis order of the proteolysis sites of V-CL was investigated and compared with the predicted stability profile. The experimentally determined proteolysis order agreed with the predicted stability profile, suggesting that the proteolysis order of these proteolysis sites was determined by their structural stability. This work is among the pioneer studies on establishing a correlation between the order of proteolysis and the predicted protein stability profile of collagens and CL proteins. Since the digestion of collagen is frequently linked to disease states, this study can potentially shed light on the biodegradation pathway of collagens and related disease models. Moreover, as collagens have been used in drug delivery, this work can provide the molecular basis for rational design of CL proteins with varied biostability.