The occluding loop of Cathepsin B prevents its effective inhibition by human kininogens

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DOIResolve DOI: http://doi.org/10.1016/j.jmb.2010.06.006
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TypeArticle
Journal titleJournal of Molecular Biology
Volume400
Issue5
Pages10221035; # of pages: 14
SubjectCysteine protease; Cystatin; Kininogen; Protease inhibitor; Proteolysis
AbstractKininogens, the major plasma cystatin-like inhibitors of cysteine cathepsins are degraded at sites of inflammation, and cathepsin B has been identified as a prominent mediator of this process. Cathepsin B, in contrast to cathepsins L and S, is poorly inhibited by kininogens. This led us to delineate the molecular interactions between this protease and kininogens (high molecular weight kininogen and low molecular weight kininogen) and to elucidate the dual role of the occluding loop in this weak inhibition. Cathepsin B cleaves high molecular weight kininogen within the N-terminal region of the D2 and D3 cystatin-like domains and close to the consensus QVVAG inhibitory pentapeptide of the D3 domain. The His110Ala mutant, unlike His111Ala cathepsin B, fails to hydrolyze kininogens, but rather forms a tight-binding complex as observed by gel-filtration analysis. Ki values (picomolar range) as well as association rate constants for the His110Ala cathepsin B variant compare to those reported for cathepsin L for both kininogens. Homology modeling of isolated inhibitory (D2 and D3) domains and molecular dynamics simulations of the D2 domain complexed with wild-type cathepsin B and its mutants indicate that additional weak interactions, due to the lack of the salt bridge (Asp22-His110) and the subsequent open position of the occluding loop, increase the inhibitory potential of kininogens on His110Ala cathepsin B.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Biotechnology Research Institute
Peer reviewedYes
NRC number53124
NPARC number16512459
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Record identifier103e4b49-5312-4f3f-934e-0cac077ad726
Record created2010-12-14
Record modified2016-05-09
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