3M81

Crystal structure of Acetyl xylan esterase (TM0077) from THERMOTOGA MARITIMA at 2.50 A resolution (native apo structure)

Summary for 3M81

• Entry DOI: 10.2210/pdb3m81/pdb
• Related: 1VLQ 3M82 3M83
• Descriptor: Acetyl xylan esterase, CALCIUM ION, CHLORIDE ION, ... (6 entities in total)
• Functional Keywords: structural genomics, joint center for structural genomics, jcsg, protein structure initiative, psi-2, axe1, hydrolase
• Biological source: Thermotoga maritima
• Total number of polymer chains: 6
• Total formula weight: 233122.48

Authors

Joint Center for Structural Genomics (JCSG) (deposition date: 2010-03-17, release date: 2010-04-21, Last modification date: 2023-09-20)

Primary citation

Levisson, M.,Han, G.W.,Deller, M.C.,Xu, Q.,Biely, P.,Hendriks, S.,Ten Eyck, L.F.,Flensburg, C.,Roversi, P.,Miller, M.D.,McMullan, D.,von Delft, F.,Kreusch, A.,Deacon, A.M.,van der Oost, J.,Lesley, S.A.,Elsliger, M.A.,Kengen, S.W.,Wilson, I.A.
Functional and structural characterization of a thermostable acetyl esterase from Thermotoga maritima.
Proteins, 80:1545-1559, 2012

PubMed Abstract: 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 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 and paraoxon were determined to 2.4 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 Ser hydroxyl rotation prevents reversal of the reaction and allows access of a water molecule for completion of the reaction.

PubMed: 22411095
DOI: 10.1002/prot.24041

Experimental method

X-RAY DIFFRACTION (2.5 Å)