Atomic resolution structure of squash trypsin inhibitor: unexpected metal coordination.Thaimattam, R., Tykarska, E., Bierzynski, A., Sheldrick, G.M., Jaskolski, M.
(2002) Acta Crystallogr.,Sect.D 58: 1448-1461
- PubMed: 12198301
- DOI: 10.1107/S0907444902011769
- PubMed Abstract:
- Conservative mutation Met8 --> Leu Effects Folding and Stability of Squash Trypsin Inhibitor Cmti-I
Zhukov, I.,Jaroszewski, L.,Bierzynski, A.
(2000) Protein Sci. 9: 273
- The refined 2.0 A X-ray crystal structure of the complex formed between bovine beta-trypsin and CMTI-I, a trypsin inhibitor from squash seeds (Cucurbita maxima). Topological similarity of the squash seed inhibitors with the carboxypeptidase A inhibitor from potatoes
Bode, W.,Greyling, H.J.,Huber, R.,Otlewski, J.,Wilusz, T.
(1989) FEBS Lett. 242: 285
- High-Resolution Structures of Three New Trypsin-Squash-Inhibitor Complexes: A Detailed Comparison with Other Trypsins and Their Complexes
Helland, R.,Berglund, G.I.,Otlewski, J.,Apostoluk, W.,Andersen, O.A.,Willassen, N.P.,Smalas, A.O.
(1999) Acta Crystallogr.,Sect.D 55: 139
- Relaxation matrix refinement of the solution structure of squash trypsin inhibitor
Nilges, M.,Habazettl, J.,Brunger, A.T.,Holak, T.A.
(1991) J.Mol.Biol. 219: 499
CMTI-I, a small-protein trypsin inhibitor, has been crystallized as a 4:1 protein-zinc complex. The metal is coordinated in a symmetric tetrahedral fashion by glutamate/glutamic acid side chains. The structure was solved by direct methods in the abse ...
CMTI-I, a small-protein trypsin inhibitor, has been crystallized as a 4:1 protein-zinc complex. The metal is coordinated in a symmetric tetrahedral fashion by glutamate/glutamic acid side chains. The structure was solved by direct methods in the absence of prior knowledge of the special position metal centre and refined with anisotropic displacement parameters using diffraction data extending to 1.03 A. In the final calculations, the main-chain atoms of low B(eq) values were refined without restraint control. The two molecules in the asymmetric unit have a conformation that is very similar to that reported earlier for CMTI-I in complex with trypsin, despite the Met8Leu mutation of the present variant. The only significant differences are in the enzyme-binding epitope (including the Arg5 residue) and in a higher mobility loop around Glu24. The present crystal structure contains organic solvent molecules (glycerol, MPD) that interact with the inhibitor molecules in an area that is at the enzyme-inhibitor interface in the CMTI-I-trypsin complex. A perfectly ordered residue (Ala18) has an unusual Ramachandran conformation as a result of geometrical strain introduced by the three disulfide bridges that clamp the protein fold. The results confirm deficiencies of some stereochemical restraints, such as peptide planarity or the N-C(alpha)-C angle, and suggest a link between their violations and hydrogen bonding.
Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland.