title: Crystal structure of human cystatin D, a cysteine peptidase inhibitor with restricted inhibition profile.
abstract: Cystatins are natural inhibitors of papain-like (family C1) and legumain-related (family C13) cysteine peptidases. Cystatin D is a type 2 cystatin, a secreted inhibitor found in human saliva and tear fluid. Compared with its homologues, cystatin D presents an unusual inhibition profile with a preferential inhibition cathepsin S > cathepsin H > cathepsin L and no inhibition of cathepsin B or pig legumain. To elucidate the structural reasons for this specificity, we have crystallized recombinant human Arg(26)-cystatin D and solved its structures at room temperature and at cryo conditions to 2.5- and 1.8-A resolution, respectively. Human cystatin D presents the typical cystatin fold, with a five-stranded anti-parallel beta-sheet wrapped around a five-turn alpha-helix. The structures reveal differences in the peptidase-interacting regions when compared with other cystatins, providing plausible explanations for the restricted inhibitory specificity of cystatin D for some papain-like peptidases and its lack of reactivity toward legumain-related enzymes.
authors.affiliation: Department of Clinical Chemistry, Institute of Laboratory Medicine, Lund University, SE-221 85 Lund, Sweden.
authors.forename: Marcia
authors.initials: M
authors.lastname: Alvarez-Fernandez
authors.forename: Yu-He
authors.initials: YH
authors.lastname: Liang
authors.forename: Magnus
authors.initials: M
authors.lastname: Abrahamson
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002401:Cathepsin B / Q000378:metabolism; D056655:Cathepsin H; D056668:Cathepsin L; D002403:Cathepsins / Q000037:antagonists & inhibitors; D003460:Crystallization; D018360:Crystallography, X-Ray; D015891:Cystatins / Q000737:chemistry* / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000494:pharmacology; D013552:Swine; D000099240:Asparaginyl Endopeptidase
chemical_list: D002401:Cathepsin B; D056655:Cathepsin H; D056668:Cathepsin L; D002403:Cathepsins; D015891:Cystatins; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins; D000099240:Asparaginyl Endopeptidase; C071378:CST5 protein, human; C534281:CTSL protein, human; C534126:CTSH protein, human; C028217:cathepsin S