COLLAGEN-II CONTAINING A CYS SUBSTITUTION FOR ARG-ALPHA-1-519 - HOMOTRIMERIC MONOMERS CONTAINING THE MUTATION DO NOT ASSEMBLE INTO FIBRILS BUT ALTER THE SELF-ASSEMBLY OF THE NORMAL-PROTEIN

A recombinant system was used to prepare human type II procollagen con taining the substitution of Cys for Arg at alpha 1-519 found in three unrelated families with early onset generalized osteoarthritis togethe r with features of a mild chondrodysplasia probably best classified as spondyloepiphyseal dysplasia. In contrast to mutated procollagens con taining Cys substitutions for obligatory Gly residues, the Cys substit ution at alpha 1-519 did not generate any intramolecular disulfide bon ds. The results were consistent with computer modeling experiments tha t demonstrated that the alpha carbon distances were shorter with Cys s ubstitutions for obligatory Gly residues than with Cys substitutions i n the Y position residues in repeating -G1S-X-Y- sequences of the coll agen triple helix. The mutated collagen did not assemble into fibrils under conditions in which the normal monomers polymerized. However, th e presence of the mutated monomer in mixtures with normal collagen II increased the lag time for fibril assembly and altered the morphology of the fibrils formed.