Site-directed mutagenesis of a conserved Asn450 residue of Bacillus licheniformis γ-glutamyltranspeptidase.

Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) belongs to N-terminal nucleophile hydrolase superfamily in which all inclusive members are synthetized as single-chain precursors, and then self-processed to form mature enzymes. Here we investigated the role of a conserved Asn450 residue in BlGGT through site-directed mutagenesis and molecular characterization of four relevant variants. Substitution of Asn450 by arginine resulted in a significant reduction in the catalytic activity of BlGGT.

Gene expression and molecular characterization of a chaperone protein HtpG from Bacillus licheniformis.

Heat shock protein 90 (Hsp90/HtpG) is a highly abundant and ubiquitous ATP-dependent molecular chaperone consisting of three flexibly linked regions, an N-terminal nucleotide-binding domain, middle domain, and a C-terminal domain. Here the putative htpG gene of Bacillus licheniformis was cloned and heterologously expressed in Escherichia coli M15 cells. Native-gel electrophoresis, size exclusion chromatography, and cross-linking analysis revealed that the recombinant protein probably exists as a mixture of monomer, dimer and other oligomers in solution.