SUBSTRATE-BINDING SPECIFICITY OF HSP47, A PROCOLLAGEN-SPECIFIC MOLECULAR CHAPERONE

概要

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HSP47 is a procollagen-specific molecular chaperone that resides in the endoplasmic reticulum (ER) of collagen producing cells. This protein specifically interacts with various types of procollagen in the ER. Recent in vivo study utilizing the gene knockout technique clearly indicated that HSP47 is essential to normal procollagen biosynthesis by demonstrating severe impairments of various collagen-based tissue structures in the embryonic lethal hsp47 null mice (Nagai et al., J. Cell. Bid. 2000). To clarify the molecular mechanism of HSP47 function, precise analysis of substrate (procollagen) - chaperone (HSP47) interaction is particularly important. In this presentation, we will show the recent progress in our study on procollagen recognition by HSP47. We have revealed that Xaa-Arg-Gly triplets in the collagen triple helix form dominant HSP47-binding sites using collagen model peptides and chemically modified collagens. Binding of HSP47 to the Xaa-Arg-Gly sequence was much stronger than that to previously identified (Pro-Pro-Gly)_n sequence (Koide et al, J.B,ol. Chem. 1999). Based on the data, we can now predict the possible binding sites for HSP47 in homotrimeric procollagen molecules. A possible role of HSP47 in procollagen folding within the ER will be also discussed.
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