The 1.6 Å structure of Kunitz-type domain from the α3 chain of human type VI collagen

• Published in: Journal of molecular biology Vol. 246; no. 5; pp. 609 - 617
• Main Authors: Arnoux, Bernadette, Mérigeau, Karine, Saludjian, Pedro, Norris, Fanny, Norris, Kjeld, Bjørn, Søren, Olsen, Ole, Petersen, Lars, Ducruix, Arnaud
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1995
• Subjects: APPI; BPTI; collagen; Kunitz domain; X-ray; APPI; collagen; APPH; X-ray; BPTI; TFPI; Kunitz domain; PCR
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/S0022-2836(05)80110-X

The C-terminal Kunitz-type domain from the α3 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 monoclinic form, space group
P2
1, with
a = 25.7 Å,
b = 38.2 Å,
c = 28.8 Å and β = 109°. 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 Å. 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 Cyauthor4-Cy8 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.