Purification, characterization and preliminary X-ray diffraction analysis of a cold-active lipase (CpsLip) from the psychrophilic bacterium Colwellia psychrerythraea 34H

Abstract

The putative lipase CpsLip from the psychrophilic bacterium Colwellia psychrerythraea 34H encodes a 34 538 Da, 308-amino-acid protein. In this study, CpsLip (UniProtKB code Q486T5) was expressed as an N-terminal hexahistidine fusion protein in Escherichia coli and purified by affinity and size-exclusion chromatography. The expression and purification of CpsLip enabled characterization of the lipase enzymatic properties of the protein. The optimal activity temperature and pH of the recombinant protein were 298 K and pH 7, respectively. CpsLip maintained over 80% activity in the low-temperature range (278-288 K), thereby suggesting that CpsLip is a cold-active lipase. Substrate-specificity analysis demonstrated that CpsLip exhibits maximum activity towards the C12 acyl group. In addition, sequence-alignment results revealed that CpsLip has a highly conserved catalytic triad in the active site consisting of residues Ser111, Asp135 and His283. Moreover, purified CpsLip was successfully crystallized using the hanging-drop vapour-diffusion method and a complete diffraction data set was collected to 4.0 angstrom resolution using synchrotron radiation on the BL-5A beamline of the Photon Factory.