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J. Bacteriol., Jan 1996, 68-77, Vol 178, No. 1
HF Jenkinson, RA Baker and GW Tannock
Cells of the oral bacterium Streptococcus gordonii express three
cytoplasmic membrane-bound lipoproteins with apparent molecular masses of
76 to 78 kDa that are the products of three genes (designated hppA, hppG,
and hppH). The lipoproteins are immunologically cross-reactive, contain 60%
or more identical amino acid residues, and are highly similar to the AmiA,
AliA (PlpA), and AliB substrate-binding protein components of an
oligopeptide permease in Streptococcus pneumoniae. Insertional inactivation
of the hppA or hppH gene resulted in loss of the ability of S. gordonii
cells to utilize specific peptides of five to seven amino acid residues for
growth. An insertion within the COOH- terminal coding region of hppG that
caused apparent truncation of the HppG polypeptide had a similar effect;
however, S. gordonii mutants in which HppG polypeptide production was
abolished were still able to grow on all oligopeptides tested. Inactivation
of hppA gene (but not inactivation of the hppG or hppH gene) caused reduced
growth rate of cells in complex medium, slowed the rate of development of
competence for transformation, reduced the efficiency of transformation,
and increased the resistance of cells to aminopterin. These results suggest
that the formation of a solute-binding-protein complex consisting of at
least the HppA and the HppH lipopolypeptides is necessary for binding and
subsequent uptake of primarily hexa- or heptapeptides by a Hpp
(Hexa-heptapeptide permease) system in S. gordonii. In addition, Hpp may
play a role in the control of metabolic functions associated with the
growth of streptococcal cells on complex nitrogen sources and with the
development of competence.
Copyright © 1996, American Society for Microbiology
A binding-lipoprotein-dependent oligopeptide transport system in Streptococcus gordonii essential for uptake of hexa- and heptapeptides
Department of Oral Biology and Oral Pathology, University of Otago, Dunedin, New Zealand.
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