H. Chanut-delalande et al., Control of heterotypic fibril formation by collages V is determined by chain stoichiometry, J BIOL CHEM, 276(26), 2001, pp. 24352-24359
Although the collagen V heterotrimer is known to be involved in the control
of fibril assembly, the role of the homotrimer in fibrillar organization h
as not yet been examined. Here, the production of substantial amounts of re
combinant collagen V homotrimer has allowed a detailed study of its role in
homotypic and heterotypic fibril formation. After removal of terminal regi
ons by pepsin digestion, both the collagen V heterotrimer and homotrimer fo
rmed thin homotypic fibrils, thus showing that diameter limitation is at le
ast in part an intrinsic property of the collagen V triple helix. When mixe
d with collagen I, however, various complementary approaches indicated that
the collagen V heterotrimer and homotrimer exerted different effects in he
terotypic fibril formation. Unlike the heterotrimer, which was buried in th
e fibril interior, the homotrimer was localized as thin filamentous structu
res at the surface of wide collagen I fibrils and did not regulate fibril a
ssembly. Its localization at the fibril surface suggests that the homotrime
r can act as a molecular linker between collagen fibrils or macromolecules
in the extracellular matrix or both. Thus, depending on their respective di
stribution in tissues, the different collagen V isoforms might fulfill spec
ific biological functions.