Bacterial collagen-binding domain targets undertwisted regions of collagen

by Philominathan, Sagaya Theresa Leena; Koide, Takaki; Matsushita, Osamu; Sakon, Josh

Clostridium histolyticum collagenase causes extensive degradation of collagen in connective tissue that results in gas gangrene. The C-terminal collagen-binding domain (CBD) of these enzymes is the minimal segment required to bind to a collagen fibril. CBD binds unidirectionally to the undertwisted C-terminus of triple helical collagen. Here, we examine whether CBD could also target undertwisted regions even in the middle of the triple helix. Collageneous peptides with an additional undertwisted region were synthesized by introducing a Gly ? Ala substitution [(POG)xPOA(POG)y]3, where x + y = 9 and x > 3). 1H15N heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) titration studies with 15N-labeled CBD demonstrated that the minicollagen binds to a 10 angstrom wide 25 angstrom long cleft. Six collagenous peptides each labeled with a nitroxide radical were then titrated with 15N-labeled CBD. CBD binds to either the Gly ? Ala substitution site or to the C-terminus of each minicollagen. Small-angle X-ray scattering measurements revealed that CBD prefers to bind the Gly ? Ala site to the C-terminus. The HSQC NMR spectra of 15N-labeled minicollagen and minicollagen with undertwisted regions were unaffected by the titration of unlabeled CBD. The results imply that CBD binds to the undertwisted region of the minicollagen but does not actively unwind the triple helix.

Journal
Protein Science
Volume
21
Issue
10
Year
2012
Start Page
1554
ISBN/ISSN
1469-896X; 0961-8368
PMID
22898990
DOI
10.1002/pro.2145