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J. Bacteriol., 05 1997, 3310-3316, Vol 179, No. 10
MS Turner, P Timms, LM Hafner and PM Giffard
Extraction of Lactobacillus fermentum BR11 cells with 5 M LiCl yielded a
preparation containing a single predominant polypeptide with an apparent
molecular mass of 32 kDa. A clone encoding an immunoreactive 32-kDa
polypeptide was isolated from a pUC18 library of L. fermentum BR11 DNA by
screening with an antiserum raised against whole cells of L. fermentum
BR11. Sequence determination of the insert in the clone revealed a complete
795-bp open reading frame (ORF) that defines a 28,625-Da polypeptide
(BspA). N-terminal sequencing of the LiCl- extracted polypeptide from L.
fermentum BR11 confirmed that it is the same as the cloned BspA. BspA was
found to have a sequence similar to those of family III of the bacterial
solute-binding proteins. The sequences of two ORFs upstream of bspA are
consistent with bspA being located in an operon encoding an ATP-binding
cassette-type uptake system. Unusually, BspA contains no lipoprotein
cleavage and attachment motif (LXXC), despite its origin in a gram-positive
bacterium. Biotin labelling and trypsin digestion of whole cells indicated
that this polypeptide is exposed on the cell surface. The isoelectric point
as predicted from the putative mature sequence is 10.59. It was
consequently hypothesized that the positively charged BspA is anchored by
electrostatic interaction with acidic groups on the cell surface. It was
shown that BspA could be selectively removed from the surface by extraction
with an acidic buffer, thus supporting this hypothesis.
Copyright © 1997, American Society for Microbiology
Identification and characterization of a basic cell surface-located protein from Lactobacillus fermentum BR11
Centre for Molecular Biotechnology, School of Life Science, Queensland University of Technology, Brisbane, Australia.
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