HSP47 binds cooperatively to triple helical type I collagen but has littleeffect on the thermal stability or rate of refolding

HSP47, a collagen-specific molecular chaperone, interacts with unfolded and folded procollagens. Binding of chicken HSP47 to native bovine type I coll agen was studied by fluorescence quenching and cooperative binding with a c ollagen concentration at half saturation (K-half) of 1.4 x 10(-7) M, and a Hill coefficient of 4.3 was observed. Similar results are observed for the binding of mouse HSP47 recombinantly expressed in Escherichia coli, Chicken HSP47 binds equally well to native type II and type III procollagen withou t the carboxyl-terminal propeptide (pN type III collagen), but binding to t riple helical collagen-like peptides is much weaker. Weak binding occurred to both hydroxylated and nonhydroxylated collagen-like peptides, and a sign ificant chain length dependence was observed. Binding of HSP47 to native ty pe I collagen had no effect on the thermal stability of the triple helix. R efolding of type I collagen in the presence of HSP47 showed minor changes, but these are probably not biologically significant. Binding of HSP47 to bo vine pN type III collagen has only minor effects on the thermal stability o f the triple helix and does not influence the refolding kinetics of the tri ple helix.