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J. Bacteriol., Feb 1996, 823-830, Vol 178, No. 3
AR Reeves, JN D'Elia, J Frias and AA Salyers
Previous studies suggested that the first step in utilization of starch by
Bacteroides thetaiotaomicron was binding of the polysaccharide to the cell
surface, followed by translocation of the polysaccharide across the outer
membrane into the periplasm. In this study, we report the molecular
characterization of a gene that encodes an outer membrane protein that is
essential for utilization of both maltooligosaccharides and starch. The
gene, susC, encoded a protein of 115.3 kDa. Antibodies were raised against
SusC, and the outer membrane location of SusC could be confirmed by Western
blot (immunoblot) analysis. SusC had a possible signal sequence of between
20 and 39 amino acids, depending on which N- terminal methionine initiates
the start of the protein. It also had some features typical of
well-characterized outer membrane proteins from members of the family
Enterobacteriaceae, such as a terminal phenylalanine residue and a region
in the amino portion of the protein thought to be involved in stabilizing
the protein in the outer membrane. The amino acid sequence, together with
results of gene disruption experiments, suggested that SusC was not an
amylolytic enzyme. Transcriptional fusion experiments, using
beta-glucuronidase as a reporter group, showed that expression of susC was
maltose regulated at the transcriptional level. This is the first molecular
characterization of a B. thetaiotaomicron outer membrane protein involved
in maltooligosaccharide and starch utilization.
Copyright © 1996, American Society for Microbiology
A Bacteroides thetaiotaomicron outer membrane protein that is essential for utilization of maltooligosaccharides and starch
Department of Microbiology, University of Illinois, Urbana 61801, USA.
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