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PDBsum entry 1cso
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Hydrolase/hydrolase inhibitor
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PDB id
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1cso
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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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.
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Authors
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K.S.Bateman,
S.Anderson,
W.Lu,
M.A.Qasim,
M.Laskowski,
M.N.James.
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Ref.
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Protein Sci, 2000,
9,
83-94.
[DOI no: ]
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PubMed id
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Abstract
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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.
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