Biochemical and Biophysical Research Communications, Vol.520, No.3, 538-543, 2019
Structural insight into the carboxylesterase BioH from Klebsiella pneumoniae
The BioH carboxylesterase which is a typical alpha/beta-hydrolase enzyme involved in biotin synthetic pathway in most bacteria. BioH acts as a gatekeeper and blocks the further elongation of its substrate. In the pathogen Klebsiella pneumoniae, BioH plays a critical role in the biosynthesis of biotin. To better understand the molecular function of BioH, we determined the crystal structure of BioH from K. pneumoniae at 2.26 angstrom resolution using X-ray crystallography. The structure of KpBioH consists of an alpha-beta-alpha sandwich domain and a cap domain. B-factor analysis revealed that the alpha-beta-alpha sandwich domain is a rigid structure, while the loops in the cap domain shows the structural flexibility. The active site of KpBioH contains the catalytic triad (Ser82-Asp207-His235) on the interface of the alpha-beta-alpha sandwich domain, which is surrounded by the cap domain. Size exclusion chromatography shows that KpBioH prefers the monomeric state in solution, whereas two-fold symmetric dimeric formation of KpBioH was observed in the asymmetric unit, the conserved Cys31-based disulfide bonds can maintain the irreversible dimeric formation of KpBioH. Our study provides important structural insight for understanding the molecular mechanisms of KpBioH and its homologous proteins. (C) 2019 Elsevier Inc. All rights reserved.