1c9p
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COMPLEX OF BDELLASTASIN WITH PORCINE TRYPSIN
OverviewOverview
The serine proteinase plasmin is, together with tissue-type plasminogen, activator (tPA) and urokinase-type plasminogen activator (uPA), involved, in the dissolution of blood clots in a fibrin-dependent manner. Moreover, plasmin plays a key role in a variety of other activation cascades such as, the activation of metalloproteinases, and has also been implicated in, wound healing, pathogen invasion, cancer invasion and metastasis. The, leech-derived (Hirudo medicinalis) antistasin-type inhibitor bdellastasin, represents a specific inhibitor of trypsin and plasmin and thus offers a, unique opportunity to evaluate the concept of plasmin inhibition. The, complexes formed between bdellastasin and bovine as well as porcine, beta-trypsin have been crystallised in a monoclinic and a tetragonal, crystal form, containing six molecules and one molecule per asymmetric, unit, respectively. Both structures have been solved and refined to 3.3 A, and 2.8 A resolution. Bdellastasin turns out to have an antistasin-like, fold exhibiting a bis-domainal structure like the tissue kallikrein, inhibitor hirustasin. The interaction between bdellastasin and trypsin is, restricted to the C-terminal subdomain of bdellastasin, particularly to, its primary binding loop, comprising residues Asp30-Glu38. The reactive, site of bdellastasin differs from other antistasin-type inhibitors of, trypsin-like proteinases, exhibiting a lysine residue instead of an, arginine residue at P1. A model of the bdellastasin-microplasmin complex, has been created based on the X-ray structures. Our modelling studies, indicate that both trypsin and microplasmin recognise bdellastasin by, interactions which are characteristic for canonically binding proteinase, inhibitors. On the basis of our three-dimensional structures, and in, comparison with the tissue-kallikrein-bound and free hirustasin and the, antistasin structures, we postulate that the binding of the inhibitors, toward trypsin and plasmin is accompanied by a switch of the primary, binding loop segment P5-P3. Moreover, in the factor Xa inhibitor, antistasin, the core of the molecule would prevent an equivalent rotation, of the P3 residue, making exosite interactions of antistasin with factor, Xa imperative. Furthermore, Arg32 of antistasin would clash with Arg175 of, plasmin, thus impairing a favourable antistasin-plasmin interaction and, explaining its specificity.
About this StructureAbout this Structure
1C9P is a Protein complex structure of sequences from Hirudo medicinalis and Sus scrofa with CA as ligand. Active as Trypsin, with EC number 3.4.21.4 Full crystallographic information is available from OCA.
ReferenceReference
Structure of the complex of the antistasin-type inhibitor bdellastasin with trypsin and modelling of the bdellastasin-microplasmin system., Rester U, Bode W, Moser M, Parry MA, Huber R, Auerswald E, J Mol Biol. 1999 Oct 15;293(1):93-106. PMID:10512718
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