Crystallization and preliminary X‐ray crystallographic analysis of EstE1, a new and thermostable esterase cloned from a metagenomic library

EstE1, a new thermostable esterase, was isolated by functional screening of a metagenomic DNA library from thermal environment samples. This enzyme showed activity towards short‐chain acyl derivatives of length C4–C6 at a temperature of 303–363 K and displayed a high thermostability above 353 K. EstE1 has 64 and 57% amino‐acid sequence similarity to est pc ‐encoded carboxylesterase from Pyrobaculum calidifontis and AFEST from Archaeoglobus fulgidus , respectively. The recombinant protein with a histidine tag at the C‐terminus was overexpressed in Escherichia coli strain BL21(DE3) and then purified by affinity chromatography. The protein was crystallized at 290 K by the hanging‐drop vapour‐diffusion method. X‐ray diffraction data were collected to 2.3 Å resolution from an EstE1 crystal; the crystal belongs to space group P 4 1 2 1 2, with unit‐cell parameters a = b = 73.71, c = 234.23 Å. Assuming the presence of four molecules in the asymmetric unit, the Matthews coefficient V M is calculated to be 2.2 Å 3  Da −1 and the solvent content is 44.1%.