Appl. Environ. Microbiol., Feb 1997, 355-363, Vol 63, No. 2
X Lai, FC Davis, RB Hespell and LO Ingram
Genomic libraries from nine cellobiose-metabolizing bacteria were screened
for cellobiose utilization. Positive clones were recovered from six
libraries, all of which encode phosphoenolpyruvate:carbohydrate
phosphotransferase system (PTS) proteins. Clones from Bacillus subtilis,
Butyrivibrio fibrisolvens, and Klebsiella oxytoca allowed the growth of
recombinant Escherichia coli in cellobiose-M9 minimal medium. The K.
oxytoca clone, pLOI1906, exhibited an unusually broad substrate range
(cellobiose, arbutin, salicin, and methylumbelliferyl derivatives of
glucose, cellobiose, mannose, and xylose) and was sequenced. The insert in
this plasmid encoded the carboxy-terminal region of a putative regulatory
protein, cellobiose permease (single polypeptide), and
phospho-beta-glucosidase, which appear to form an operon (casRAB).
Subclones allowed both casA and casB to be expressed independently, as
evidenced by in vitro complementation. An analysis of the translated
sequences from the EIIC domains of cellobiose, aryl-beta-glucoside, and
other disaccharide permeases allowed the identification of a 50-amino-acid
conserved region. A disaccharide consensus sequence is proposed for the
most conserved segment (13 amino acids), which may represent part of the
EIIC active site for binding and phosphorylation.
Copyright © 1997, American Society for Microbiology
Cloning of cellobiose phosphoenolpyruvate-dependent phosphotransferase genes: functional expression in recombinant Escherichia coli and identification of a putative binding region for disaccharides
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611, USA.
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