1kig
From Proteopedia
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BOVINE FACTOR XA
Overview
The structure of recombinant tick anticoagulant peptide (rTAP) complexed to bovine factor Xa at 3.0 A resolution reveals the structural basis for the specificity and the high affinity of rTAP. Three N-terminal residues, Tyr501, Asn502 and Arg503, play a critical role in the complex formation as suggested by earlier mutagenic studies and the ornithodorin-thrombin complex. Unexpectedly, the side-chain of Tyr501 is located in the S1 pocket, although factor Xa favors arginine as a P1 residue. Arg503 is located at the aryl binding pocket and forms a salt-bridge with Glu97 of factor Xa. The autolysis loop, which is disordered in the uninhibited factor Xa structure, is involved in the formation of the complex as a part of the secondary binding site. The C-terminal helix of rTAP interacts with factor Xa as a secondary binding determinant. The N-terminal residues of rTAP reorganize during the formation of the factor Xa-rTAP complex from the conformation found in the solution into an extended conformation. The presence of the secondary binding site confirms the proposed two-step kinetic mechanism based on the results of a mutagenesis study.
About this Structure
1KIG is a Protein complex structure of sequences from Bos taurus and Ornithodoros moubata. Active as Coagulation factor Xa, with EC number 3.4.21.6 Full crystallographic information is available from OCA.
Reference
Unexpected binding mode of tick anticoagulant peptide complexed to bovine factor Xa., Wei A, Alexander RS, Duke J, Ross H, Rosenfeld SA, Chang CH, J Mol Biol. 1998;283(1):147-54. PMID:9761680
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