Distinction between Two Molecular Species of Type V Collagen from Human Post-Burn Granulation Tissues

Human type V collagen was purified form post-burn granulation tissues, and was demonstrated to exist in two different molecular assemblies consisting of [α1 (V)]2α2(V) and α1(V)α2(V)α3(V) heterotrimers which are designated as type V (112) and V(123) collagens, respectively, in this paper. Two two molecular species were separated by salt fractionation at neutral pH under non-denaturing conditions. When crude type V collagen was dialyzed against phosphate-buffered saline at 4°C, mainly collagen V(112) precipitated, leaving collagen V(123) in the solution, Type V(112) collagen, but not type V (123), precipitated at 0.15 M NaCl in 50 mM Tris-HCI buffer (pH 7.5), whereas the type V(123) molecule precipitated at 4.5 M NaCI in the same buffer. when the crude type V collagen was electrophoresed under non-denaturing conditions, tow bands were observed; and it was confirmed that the fast-migrating band was composed of [α1(V)]2α2(V) and the slow-migrating band was α1(V)α2(V)α3(V). Both α1 and α2 chains of V(112) showed biochemical properties that were very similar, if not identical, to those of the corresponding α chains of V(123) judging from amino acid compositions, peptide mapping patterns obtained following treatment with cyanogen bromide and lysyl endopeptidase, and periodic acid Schiff and concanavalin A stainings. Alpha 3 chain, in contrast, was distinct from both α1 and α2 chains. The amino acid composition and peptide maps of α3 chain were similar to some extent, but not identical, to those of the α1 chain. The intensity of carbohydrate stainings of the α3 chain was clearly different form that of the α1 chain. The negatively stained segment-long-spacing crystallites of the two molecular species exhibited an identical banding pattern. The crystallite derived from collagen V(112) was usually in a dimeric form exhibiting the C-C terminal junction, but that of collagen V(123) was mostly in a monomeric form. Differences between the two molecular species is ascribed to the presence of the α3 chain in collagen V(123)