title: The 1.6 A structure of Kunitz-type domain from the alpha 3 chain of human type VI collagen.
abstract: The C-terminal Kunitz-type domain from the alpha 3 chain of human type VI collagen (C5), a single 58 amino acid residue chain with three disulfide bridges, was cloned, expressed and crystallized in a monoclonic form, space group P2(1), with a = 25.7 A, b = 38.2 A, c = 28.8 A and beta = 109 degrees. The structure was resolved by molecular replacement, using Alzheimer's protein precursor inhibitor and bovine pancreatic trypsin inhibitor three-dimensional structures as search models. The molecule with one sulfate ion and 43 associated water molecules was refined by XPLOR to an R-factor of 18.9% at 1.6 A. The molecule was not degraded by trypsin and did not inhibit trypsin or tested serine proteases. As opposed to the other Kunitz family members, C5 demonstrates left-handed chirality of the Cys14-Cys38 disulfide bond. Inversion of the Thr13 carbonyl and bulky side-chains at the interface with trypsin in a model of the C5-trypsin complex may explain the lack of inhibition of trypsin.
authors.affiliation: Laboratoire de Biologie Structurale, CNRS, Gif sur Yvette, France.
authors.forename: B
authors.initials: B
authors.lastname: Arnoux
authors.forename: K
authors.initials: K
authors.lastname: Mérigeau
authors.forename: P
authors.initials: P
authors.lastname: Saludjian
authors.forename: F
authors.initials: F
authors.lastname: Norris
authors.forename: K
authors.initials: K
authors.lastname: Norris
authors.forename: S
authors.initials: S
authors.lastname: Bjørn
authors.forename: O
authors.initials: O
authors.lastname: Olsen
authors.forename: L
authors.initials: L
authors.lastname: Petersen
authors.forename: A
authors.initials: A
authors.lastname: Ducruix
mesh_terms: D000595:Amino Acid Sequence; D007611:Aprotinin / Q000737:chemistry; D001483:Base Sequence; D001665:Binding Sites; D003094:Collagen / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D010446:Peptide Fragments; D003094:Collagen; D007611:Aprotinin