Cyanogen Bromide Peptides of the Fibrillar Collagens I, III, and V and Their Mass Spectrometric Characterization: Detection of Linear Peptides, Peptide Glycosylation, and Cross-Linking Peptides Involved in Formation of Homo- and Heterotypic Fibrils

Abstract

The network of the fibrillar collagens I, III, and V, extracted from fetal calf skin and cleaved with cyanogen bromide, was studied by means of ultraviolet matrix-assisted laser desorption ionization time-of-flight mass spectrometry (UV-MALDI MS). Nearly all of the expected cyanogen bromide peptides of the different alpha chains were detected. Distinct peptides are identified that can serve as a reference signal for the individual alpha-chains. Homo- and heterotypic cross-linking patterns, some of which have not been described before for bovine collagen, are indicated by comparison of the mass spectrometric data with documented amino acid sequences. Potential cross-linking mechanisms are discussed. For example, the mass spectrometric data suggest that the formation of heterotypic I/III and I/V fibrils is substantially determined by the telo-regions of type I collagen, which are covalently connected to the corresponding helical and nonhelical cross-linking domains of adjacent molecules either by 4D or 0D-stagger bonds. The chemical nature of the cross-links can be concluded. The data also indicate a disturbed formation of heterotypic fibrils. Finally, collagen glycosylation can also be identified.