Noncollagenous NC16 Subdomains of Collagen XVII Important for Triple Helix Folding Direction

-Helical coiled coils represent the most frequent protein oligomerization in nature and they are often found in vital proteins. In this study, using collagenXVII as, a dermal-epidermal cell surface protein in the skin, we found evidence for a newly function of coiled coils in the triple helix folding in collagenXVII. Analysis of the primary sequence of collagen XVII with the COILS program, revealed two regions within the extracellular NC16a, b domains which are predicted to form coiled coil structures. One predicted coiled coil region with six heptad repeats conserved between human, mouse and chicken starts within the transmembrane (NC16b) region and extends into the extracellular NC16a domain. The amino acid residues predicted to be located within the membrane are LLLTWLLLLGLLFGL. The second predicted coiled coil region with two heptad repeats conserved between human, mouse and chicken is located within the NC16a domain close to the first collagenous domain C15 (EEVRKLKARVDELERI and RKKLMMEQENGNLR, respectivelly). After 1 (XVII) chains synthesis, and are localized in the membrane as single chains. The coiled coil structure adjacent to the transmembrane domain mediates the chain selection before folding of the triple helix can take place. The shorter predicted coiled coil region helps to align the three 1 (XVII) chains in the correct stagger. The folding of triple helical structures starts from the N-terminal and proceeds to the C-terminal end. Our data indicate that the short coiled-coil domain of amino acids plays a central role in both structural and functional regulation of collagen XVII, in addition to triple helix folding directions.