Structure of a myristoyl-ACP-specific thioesterase from Vibrio harveyi.
The crystal structure of a myristoyl acyl carrier protein specific thioesterase (C14ACP-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-A 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 alpha/beta hydrolases, although there is no detectable homology with any of its members at the amino acid sequence level. Particularly striking similarity exists between the C14ACP-TE structure and that of haloalkane dehalogenase from Xanthobacter autotrophicus. Contrary to the conclusions of earlier studies [Ferri, S. R., & Meighen, E. A. (1991) J. Biol. Chem. 266, 12852-12857] which implicated Ser77 in catalysis, the crystal structure of C14ACP-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 Ser114. Crystallographic analysis of the Ser77-->Gly mutant at 2.5-A resolution revealed no structural changes; in both cases the loop containing the residue in position 77 is disordered.(ABSTRACT TRUNCATED AT 250 WORDS)
Lawson
D M
DM
Department of Biochemistry, University of Alberta, Edmonton, Canada.
Derewenda
U
U
Serre
L
L
Ferri
S
S
Szittner
R
R
Wei
Y
Y
Meighen
E A
EA
Derewenda
Z S
ZS
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D006867:Hydrolases / Q000737:chemistry; D008049:Lipase / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D013869:Thiolester Hydrolases / Q000737:chemistry*; D014733:Vibrio / Q000201:enzymology*; D014961:X-Ray Diffraction
D011994:Recombinant Proteins; D006867:Hydrolases; D008049:Lipase; D013869:Thiolester Hydrolases; C018748:oleoyl-(acyl-carrier-protein) hydrolase; C046137:haloalkane dehalogenase