Enzymic control of collagen fibril shape.
The shape of collagen fibrils growing in vitro in a cell-free enzyme/substrate system is shown to be dependent on the enzyme/substrate (E/S) ratio. Long fibrils with tapered ends were generated by exposing pCcollagen (procollagen from which the N-propeptides had been removed) to procollagen C-proteinase (which acts by cleaving the C-propeptides from the pCcollagen, converting it to insoluble fibril-forming collagen). Tip shape profiles, established quantitatively by scanning transmission electron microscopy, depended critically on the C-proteinase/pCcollagen ratio. The finest tips occurred at low ratios, the coarsest at high ratios. All fibrils had molecules oriented with amino termini closest to the pointed ends, i.e. N,N-bipolar fibrils in which molecules change orientation abruptly at one location along the fibril. Fibrils had maximal diameter at this molecular switch region. Shape asymmetric fibrils occurred at low E/S ratios, near-shape symmetric fibrils occurred at high ratios. Fibrils generated at low E/S ratios bore the closest resemblance to those formed in vivo except that the central shaft regions of fibrils formed in vitro showed no tendency to be limited to a uniform diameter.
Holmes
D F
DF
Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, UK.
Watson
R B
RB
Chapman
J A
JA
Kadler
K E
KE
D055395:Bone Morphogenetic Protein 1; D019485:Bone Morphogenetic Proteins; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000648:ultrastructure*; D005347:Fibroblasts; D008666:Metalloendopeptidases / Q000378:metabolism*; D017348:Microscopy, Electron, Scanning Transmission; D011347:Procollagen / Q000378:metabolism
D019485:Bone Morphogenetic Proteins; D011347:Procollagen; D003094:Collagen; D008666:Metalloendopeptidases; D055395:Bone Morphogenetic Protein 1