From the fungus Aspergillus niger, we identified a new gene encoding protein EstA, a member of the alpha/beta-hydrolase fold superfamily but of unknown substrate specificity. EstA was overexpressed and its crystal structure was solved by molecular replacement using a lipase-acetylcholinesterase chimera template. The 2.1 A resolution structure of EstA reveals a canonical Ser/Glu/His catalytic triad located in a small pocket at the bottom of a large solvent-accessible, bowl-shaped cavity. Potential substrates selected by manual docking procedures were assayed for EstA activity. Consistent with the pocket geometry, preference for hydrolysis of short acyl/propyl chain substrates was found. Identification of close homologs from the genome of other fungi, of which some are broad host-range pathogens, defines EstA as the first member of a novel class of fungal esterases within the superfamily. Hence the structure of EstA constitutes a lead template in the design of new antifungal agents directed toward its pathogenic homologs.
Title: Defining substrate characteristics from 3D structure; perspective on EstA structure Schrag JD, Cygler M Ref: Structure, 12:521, 2004 : PubMed
A multifaceted approach is adopted to characterize EstA from Aspergillus niger (Bourne et al., 2004). Collectively, biophysical, bioinformatic, and biochemical analyses identify EstA as the lead member of a new class of fungal esterases within the superfamily of alpha/beta-hydrolases.
Representative scheme of Fungal_carboxylesterase_lipase structure and an image from PDBsum server
Databases
PDB-Sum
1UKC Previously Class, Architecture, Topology and Homologous superfamily - PDB-Sum server
FSSP
1UKCFold classification based on Structure-Structure alignment of Proteins - FSSP server
