Pleomorphism in type I collagen fibrils produced by persistence of the procollagen N-propeptide.
The assembly of type I collagen and type I pN-collagen was studied in vitro using a system for generating these molecules enzymatically from their immediate biosynthetic precursors. Collagen generated by C-proteinase digestion of pC-collagen formed D-periodically banded fibrils that were essentially cylindrical (i.e. circular in cross-section). In contrast, pN-collagen generated by C-proteinase digestion of procollagen formed thin, sheet-like structures that were axially D-periodic in longitudinal section, of varying lateral widths (up to several microns) and uniform in thickness (approximately 8 nm). Mixtures of collagen and pN-collagen assembled to form a variety of pleomorphic fibrils. With increasing pN-collagen content, fibril cross-sections were progressively distorted from circular to lobulated to thin and branched structures. Some of these structures were similar to fibrils observed in certain heritable disorders of connective tissue where N-terminal procollagen processing is defective. The observations are considered in terms of the hypothesis that the N-propeptides are preferentially located on the surface of a growing assembly. The implications for normal diameter control of collagen fibrils in vivo are discussed.
Hulmes
D J
DJ
Department of Biochemistry, University of Edinburgh Medical School, U.K.
Kadler
K E
KE
Mould
A P
AP
Hojima
Y
Y
Holmes
D F
DF
Cummings
C
C
Chapman
J A
JA
Prockop
D J
DJ
D003094:Collagen / Q000648:ultrastructure*; D003238:Connective Tissue / Q000648:ultrastructure*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D011347:Procollagen / Q000378:metabolism*
D011347:Procollagen; D003094:Collagen