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1.  Functional and structural characterization of a thermostable acetyl esterase from Thermotoga maritima 
Proteins  2012;80(6):1545-1559.
TM0077 from Thermotoga maritima is a member of the carbohydrate esterase family 7 and is active on a variety of acetylated compounds, including cephalosporin C. TM0077 esterase activity is confined to short-chain acyl esters (C2-C3), and is optimal around 100°C and pH 7.5. The positional specificity of TM0077 was investigated using 4-nitrophenyl-β-D-xylopyranoside monoacetates as substrates in a β-xylosidase-coupled assay. TM0077 hydrolyzes acetate at positions 2, 3 and 4 with equal efficiency. No activity was detected on xylan or acetylated xylan, which implies that TM0077 is an acetyl esterase and not an acetyl xylan esterase as currently annotated. Selenomethionine-substituted and native structures of TM0077 were determined at 2.1 Å and 2.5 Å resolution, respectively, revealing a classic α/β-hydrolase fold. TM0077 assembles into a doughnut-shaped hexamer with small tunnels on either side leading to an inner cavity, which contains the six catalytic centers. Structures of TM0077 with covalently bound phenylmethylsulfonyl fluoride (PMSF) and paraoxon were determined to 2.4 Å and 2.1 Å, respectively, and confirmed that both inhibitors bind covalently to the catalytic serine (Ser188). Upon binding of inhibitor, the catalytic serine adopts an altered conformation, as observed in other esterase and lipases, and supports a previously proposed catalytic mechanism in which this Ser hydroxyl rotation prevents reversal of the reaction and allows access of a water molecule for completion of the reaction.
doi:10.1002/prot.24041
PMCID: PMC3348966  PMID: 22411095
Acetyl esterase; Thermotoga maritima; crystal structure; α/β hydrolase; inhibitor; serine rotation
2.  Crystallization and preliminary crystallographic analysis of an esterase with a novel domain from the hyperthermophile Thermotoga maritima  
A thermostable esterase (EstA) from Thermotoga maritima was cloned and purified. Crystals of EstA and its selenomethionine derivative were grown and diffract to beyond 2.6 Å resolution at 100 K using synchrotron radiation.
A predicted esterase (EstA) with an unusual new domain from the hyperthermophilic bacterium Thermotoga maritima has been cloned and overexpressed in Escherichia coli. The purified protein was crystallized by the hanging-drop vapour-diffusion technique in the presence of lithium sulfate and polyethylene glycol 8000. Selenomethionine-substituted EstA crystals were obtained under the same conditions and three different-wavelength data sets were collected to 2.6 Å resolution. The crystal belongs to space group H32, with unit-cell parameters a = b = 130.2, c = 306.2 Å. There are two molecules in the asymmetric unit, with a V M of 2.9 Å3 Da−1 and 58% solvent content.
doi:10.1107/S174430910703953X
PMCID: PMC2376313  PMID: 17768353
esterases; Thermotoga maritima

Results 1-2 (2)