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Structural analysis of the alcohol acyltransferase protein family from C ucumis melo shows that enzyme activity depends on an essential solvent channel
Author(s) -
Galaz Sebastián,
MoralesQuintana Luis,
MoyaLeón María Alejandra,
Herrera Raúl
Publication year - 2013
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.12127
Subject(s) - acyltransferases , residue (chemistry) , molecular dynamics , docking (animal) , chemistry , enzyme , stereochemistry , active site , threonine , biochemistry , biosynthesis , serine , computational chemistry , medicine , nursing
Alcohol acyltransferases ( AAT ) play a key role in ester biosynthesis. In C ucumis melo var. cantalupensis , AAT s are encoded by a gene family of four members (Cm AAT 1–4). Cm AAT 1, Cm AAT 3 and Cm AAT 4 are capable of synthesizing esters, with Cm AAT 1 the most active. Cm AAT 2 is inactive and has an Ala268 residue instead of a threonine which is present in all other active AAT s, although the role of this residue is still unclear. The present work aims to understand the molecular mechanism involved in ester biosynthesis in melon fruit and to clarify the importance of the Ala268 residue. First, structural models for each protein were built by comparative modelling methodology. Afterwards, conformational interaction between the protein and several ligands, alcohols and acyl‐ C oAs was explored by molecular docking and molecular dynamics simulation. Structural analysis showed that Cm AAT s share a similar structure. Also, well‐defined solvent channels were described in the Cm AAT s except for Cm AAT 2 which does not have a proper channel and instead has a small pocket around Ala268. Residues of the catalytic HxxxD motif interact with substrates within the solvent channel, with Ser363 also important. Strong binding interaction energies were described for the best substrate couple of each Cm AAT (hexyl‐, benzyl‐ and cinnamyl‐acetate for Cm AAT 1, 3 and 4 respectively). Cm AAT 1 and Cm AAT 2 protein surfaces share similar electrostatic potentials; nevertheless the entrance channels for the substrates differ in location and electrostatic character, suggesting that Ala268 might be responsible for that. This could partly explain the major differences in activity reported for these two enzymes. Database Structural data have been deposited in the Protein Model Data Bank under the following accession numbers: CmAAT1 ( PM0078514 ); CmAAT2 ( PM0078515 ); CmAAT3 ( PM0078516 ); CmAAT4 ( PM0078517 )