TAILIEUCHUNG - Báo cáo khoa học: Ca2+-induced linker transformation leads to a compact and rigid collagen-binding domain of Clostridium histolyticum collagenase

Clostridium histolyticum collagenase is responsible for extensive tissue destruction in gas gangrene, and its activity is enhanced by calcium ions. The collagen-binding domain is the minimal segment of the enzyme required for binding to insoluble collagen fibrils and for subsequent colla-genolysis. | Ca2 -induced linker transformation leads to a compact and rigid collagen-binding domain of Clostridium histolyticum collagenase Sagaya T. L. Philominathan1 Osamu Matsushita2 Robert Gensure3 and Joshua Sakon1 1 Department of Chemistry and Biochemistry University of Arkansas Fayetteville AR USA 2 Department of Microbiology and Parasitology Kitasato University Medical School Kanagawa Japan 3 Ochsner Children s Hospital New Orleans LA USA Keywords Ca2 collagen-binding domain linker stability structuraltransformation Correspondence S. T. L. Philominathan Department of Chemistry and Biochemistry University of Arkansas Fayetteville AR 72701 USA Fax 1 479 575 4049 Tel 1 479 575 3181 E-mail pstleena@ Received 4 March 2009 revised 21 April 2009 accepted 30 April 2009 doi Clostridium histolyticum collagenase is responsible for extensive tissue destruction in gas gangrene and its activity is enhanced by calcium ions. The collagen-binding domain is the minimal segment of the enzyme required for binding to insoluble collagen fibrils and for subsequent colla-genolysis. The collagen-binding domain is joined to another binding module by a conserved 14-amino-acid linker. The linker undergoes secondary structural transformation from an a-helix to a b-strand and forms a nonprolyl cis-peptide in the presence of calcium ions. In this study various biophysical methods were utilized to better understand the structure and functional role of the novel calcium-activated linker. Two Ca2 ions bind cooperatively with macroscopic association constants of K1 X 105 M-1 and K2 X 105 M-1. The chelation of the second calcium ion is enthalpically unfavorable which could be a result of isomerization of the nonprolyl cis-peptide. The holo protein is more stable than the apo protein against thermal denaturation ATm 20 C and chemical denaturation AAGH2O 3 kcal-mol-1 for urea or guanidine HCl denaturation and A20 v v in 2 2 2-trifluoroethanol . The compact

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