1CSO

CRYSTAL STRUCTURE OF THE OMTKY3 P1 VARIANT OMTKY3-ILE18I IN COMPLEX WITH SGPB

Summary for 1CSO

• Entry DOI: 10.2210/pdb1cso/pdb
• Related: 1CT0 1CT2 1CT4 1SGP 1SGQ 1SGR 3SGB
• Descriptor: PROTEINASE B, OVOMUCOID INHIBITOR (3 entities in total)
• Functional Keywords: enzyme-inhibitor complex, beta-branched p1 residue, hydrolase-hydrolase inhibitor complex, hydrolase/hydrolase inhibitor
• Biological source: Meleagris gallopavo (turkey); More
• Cellular location: Secreted: P68390
• Total number of polymer chains: 2
• Total formula weight: 24250.57

Authors

Bateman, K.S.,Anderson, S.,Lu, W.,Qasim, M.A.,Laskowski Jr., M.,James, M.N.G. (deposition date: 1999-08-18, release date: 2000-01-12, Last modification date: 2011-07-13)

Primary citation

Bateman, K.S.,Anderson, S.,Lu, W.,Qasim, M.A.,Laskowski Jr., M.,James, M.N.
Deleterious effects of beta-branched residues in the S1 specificity pocket of Streptomyces griseus proteinase B (SGPB): crystal structures of the turkey ovomucoid third domain variants Ile18I, Val18I, Thr18I, and Ser18I in complex with SGPB.
Protein Sci., 9:83-94, 2000

PubMed Abstract: Turkey ovomucoid third domain (OMTKY3) is a canonical inhibitor of serine proteinases. Upon complex formation, the inhibitors fully exposed P1 residue becomes fully buried in the preformed cavity of the enzyme. All 20 P1 variants of OMTKY3 have been obtained by recombinant DNA technology and their equilibrium association constants have been measured with six serine proteinases. To rationalize the trends observed in this data set, high resolution crystal structures have been determined for OMTKY3 P1 variants in complex with the bacterial serine proteinase, Streptomyces griseus proteinase B (SGPB). Four high resolution complex structures are being reported in this paper; the three beta-branched variants, Ile18I, Val18I, and Thr18I, determined to 2.1, 1.6, and 1.7 A resolution, respectively, and the structure of the Ser18I variant complex, determined to 1.9 A resolution. Models of the Cys18I, Hse18I, and Ape18I variant complexes are also discussed. The beta-branched side chains are not complementary to the shape of the S1 binding pocket in SGPB, in contrast to that of the wild-type gamma-branched P1 residue for OMTKY3, Leu18I. Chi1 angles of approximately 40 degrees are imposed on the side chains of Ile18I, Val18I, and Thr18I within the S1 pocket. Dihedral angles of +60 degrees, -60 degrees, or 180 degrees are more commonly observed but 40 degrees is not unfavorable for the beta-branched side chains. Thr18I Ogamma1 also forms a hydrogen bond with Ser195 Ogamma in this orientation. The Ser18I side chain adopts two alternate conformations within the S1 pocket of SGPB, suggesting that the side chain is not stable in either conformation.

PubMed: 10739250

Experimental method

X-RAY DIFFRACTION (1.9 Å)