A physical and functional analysis of the newly-identified bglGPT operon of Lactobacillus plantarum

A newly-identified bbl/GPT operon of Lactobacillus plantarum was isolated a nd expressed in Escherichia coli. The sequence analysis of the cloned DNA f ragment showed three open reading frames encoding (i) a 237-amino acid prot ein (BglG), (ii) a 577-amino acid protein (BglP) and (iii) a 486-amino acid protein (BglT). BglG, BglP and BglT were shown to be homologous to the Bgl G family of transcriptional antiterminators, to permeases of the phosphoeno lpyruvate-dependent phosphotransferase system and to beta-glucosidases, res pectively. Complementation of E. coli mutant strains showed that BglP and B glT are a permease and a beta-glucosidase active on the beta-glucosides, 5- bromo-4-chloro-3-indolyl-beta-D-glucopyranoside and p-nitrophenyl-beta-D-gl ucoside, respectively. BglG was also shown to promote expression of a bglG- lacZ gene fusion in an E, coli bglG(-) background. A ribonucleic antitermin ator sequence, the antiterminator-responsive cis-element and a 'catabolite responsive element', were found downstream of the transcriptional start poi nt. Transcription of the operon was repressed 10-fold in L. plantarum cells grown on glucose as compared to ribose. (C) 2000 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V. All rights rese rved.