Weston LA

References (2)

Title : Large-scale structural rearrangement of a serine hydrolase from Francisella tularensis facilitates catalysis - Filippova_2013_J.Biol.Chem_288_10522
Author(s) : Filippova EV , Weston LA , Kuhn ML , Geissler B , Gehring AM , Armoush N , Adkins CT , Minasov G , Dubrovska I , Shuvalova L , Winsor JR , Lavis LD , Satchell KJ , Becker DP , Anderson WF , Johnson RJ
Ref : Journal of Biological Chemistry , 288 :10522 , 2013
Abstract : Tularemia is a deadly, febrile disease caused by infection by the gram-negative bacterium, Francisella tularensis. Members of the ubiquitous serine hydrolase protein family are amongst current targets to treat diverse bacterial infections. Herein, we present a structural and functional study of a novel bacterial carboxylesterase (FTT258) from F. tularensis - a homologue of human acyl protein thioesterase (hAPT1). The structure of FTT258 has been determined in multiple forms, and unexpectedly large conformational changes of a peripheral flexible loop occur in the presence of a mechanistic cyclobutanone ligand. The concomitant changes in this hydrophobic loop and the newly exposed hydrophobic substrate-binding pocket suggest that the observed structural changes are essential to the biological function and catalytic activity of FTT258. Using diverse substrate libraries, site-directed mutagenesis, and liposome binding assays, we determined the importance of these structural changes to the catalytic activity and membrane binding activity of FTT258. Residues within the newly exposed hydrophobic binding pocket and within the peripheral flexible loop proved essential to the hydrolytic activity of FTT258, indicating that structural rearrangement is required for catalytic activity. Both FTT258 and hAPT1 also showed significant association with liposomes designed to mimic bacterial or human membranes, respectively, even though similar structural rearrangements for hAPT1 have not been reported. The necessity for acyl protein thioesterases to have maximal catalytic activity near the membrane surface suggests that these conformational changes in the protein may dually regulate catalytic activity and membrane association in bacterial and human homologues.
ESTHER : Filippova_2013_J.Biol.Chem_288_10522
PubMedSearch : Filippova_2013_J.Biol.Chem_288_10522
PubMedID: 23430251
Gene_locus related to this paper: fratt-q5ni32

Title : The structural basis for the narrow substrate specificity of an acetyl esterase from Thermotoga maritima - Hedge_2012_Biochim.Biophys.Acta_1824_1024
Author(s) : Hedge MK , Gehring AM , Adkins CT , Weston LA , Lavis LD , Johnson RJ
Ref : Biochimica & Biophysica Acta , 1824 :1024 , 2012
Abstract : Acetyl esterases from carbohydrate esterase family 7 exhibit unusual substrate specificity. These proteins catalyze the cleavage of disparate acetate esters with high efficiency, but are unreactive to larger acyl groups. The structural basis for this distinct selectivity profile is unknown. Here, we investigate a thermostable acetyl esterase (TM0077) from Thermotoga maritima using evolutionary relationships, structural information, fluorescent kinetic measurements, and site directed mutagenesis. We measured the kinetic and structural determinants for this specificity using a diverse series of small molecule enzyme substrates, including novel fluorogenic esters. These experiments identified two hydrophobic plasticity residues (Pro228, and Ile276) surrounding the nucleophilic serine that impart this specificity of TM0077 for small, straight-chain esters. Substitution of these residues with alanine imparts broader specificity to TM0077 for the hydrolysis of longer and bulkier esters. Our results suggest the specificity of acetyl esterases have been finely tuned by evolution to catalyze the removal of acetate groups from diverse substrates, but can be modified by focused amino acid substitutions to yield enzymes capable of cleaving larger ester functionalities.
ESTHER : Hedge_2012_Biochim.Biophys.Acta_1824_1024
PubMedSearch : Hedge_2012_Biochim.Biophys.Acta_1824_1024
PubMedID: 22659119
Gene_locus related to this paper: thema-TM0077