title: Crystal structure of the Kunitz (STI)-type inhibitor from Delonix regia seeds.
abstract: The three-dimensional structure of a novel Kunitz (STI) family member, an inhibitor purified from Delonix regia seeds (DrTI), was solved by molecular replacement method and refined, respectively, to R(factor) and R(free) values of 21.5% and 25.3% at 1.75A resolution. The structure has a classical beta-trefoil fold, however, differently from canonical Kunitz type (STI) inhibitors, its reactive site loop has an insertion of one residue, Glu68, between the residues P1 and P2. Surprisingly, DrTI is an effective inhibitor of trypsin and human plasma kallikrein, but not of chymotrypsin and tissue kallikrein. Putative structural grounds of such specificity are discussed.
authors.affiliation: Instituto de Física de São Carlos, USP, Av. Trabalhador Saocarlense, 400, CEP 13560-970, São Carlos, SP, Brazil.
authors.forename: Sandra
authors.initials: S
authors.lastname: Krauchenco
authors.forename: Silvana C
authors.initials: SC
authors.lastname: Pando
authors.forename: Sérgio
authors.initials: S
authors.lastname: Marangoni
authors.forename: Igor
authors.initials: I
authors.lastname: Polikarpov
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods*; D007887:Fabaceae / Q000737:chemistry*; D006801:Humans; D007610:Kallikreins / Q000037:antagonists & inhibitors / Q000097:blood / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D012639:Seeds / Q000737:chemistry*; D020539:Sequence Analysis, Protein / Q000379:methods*; D014357:Trypsin / Q000737:chemistry*; D014361:Trypsin Inhibitors / Q000737:chemistry
chemical_list: C053865:Kunitz-type protease inhibitor, plant; D010455:Peptides; D010940:Plant Proteins; D014361:Trypsin Inhibitors; D007610:Kallikreins; D014357:Trypsin