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| STRUCTURE OF A MYRISTOYL-ACP-SPECIFIC THIOESTERASE FROM VIBRIO-HARVEYI |
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| Author(s): LAWSON DM, DEREWENDA U, SERRE L, FERRI S, SZITTNER R, WEI Y, MEIGHEN EA, DEREWENDA ZS |
| Source: BIOCHEMISTRY Volume: 33 Issue: 32 Pages: 9382-9388 Published: AUG 16 1994 |
| Times Cited: 82 References: 50 |
| Abstract: The crystal structure of a myristoyl acyl carrier protein specific thioesterase (C(14)ACP-TE) from a bioluminescent bacterium, Vibrio harveyi, was solved by multiple isomorphous replacement methods and refined to an R factor of 22% at 2.1-Angstrom resolution. This is the first elucidation of a three-dimensional structure of a thioesterase. The overall tertiary architecture of the enzyme resembles closely the consensus fold of the rapidly expanding superfamily of alp hydrolases, although there is no detectable homology with any of its members at the amino acid sequence level. Particularly striking similarity exists between the C(14)ACP-TE structure and that of haloalkane dehalogenase from Xanthobacter autotrophicus. Contrary to the conclusions of earlier studies [Ferri, S. R., and Meighen, E. A (1991) J. Biol. Chem. 266, 12852-12857] which implicated Ser77 in catalysis, the crystal structure of C(14)ACP-TE reveals a lipase-like catalytic triad made up of Ser114, His241, and Asp211. Surprisingly, the gamma-turn with Ser114 in a strained secondary conformation (phi = 53 degrees, psi = -127 degrees), characteristic of the so-called nucleophilic elbow, does not conform to the frequently invoked lipase/esterase consensus sequence (Gly-X-Ser-X-Gly), as the positions of both glycines are occupied by larger amino acids. Site-directed mutagenesis and radioactive labeling support the catalytic function of Ser 114. Crystallographic analysis of the Ser77 --> Gly mutant at 2.5-Angstrom resolution revealed no structural changes; in both cases the loop containing the residue in position 77 is disordered. The oxyanion hole does not appear to be fully formed in the native enzyme, suggesting that its structural reorganization may occur upon substrate binding, a mechanism reminiscent of the conformational changes underlying interfacial activation in triglyceride lipases. |
| Document Type: Article |
| Language: English |
Addresses:
1. MCGILL UNIV, DEPT BIOCHEM, MONTREAL H3G 1Y6, PQ CANADA
2. UNIV ALBERTA, DEPT BIOCHEM, MRC, PROT STRUCT & FUNCT GRP, EDMONTON T6G 2H7, AB CANADA
3. UNIV YORK, DEPT CHEM, YORK YO1 5DD, N YORKSHIRE ENGLAND |
| Publisher: AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 |
| Subject Category: Biochemistry & Molecular Biology |
| IDS Number: PC545 |
| ISSN: 0006-2960 |
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