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J. Bacteriol., 05 1997, 3188-3195, Vol 179, No. 10
DV Shevchenko, DR Akins, E Robinson, M Li, TG Popova, DL Cox and JD Radolf
Automated Edman degradation was used to obtain N-terminal and internal
amino acid sequences from a 26-kDa protein in isolated Treponema pallidum
outer membranes (OMs). The resulting sequences enabled us to PCR amplify
from T. pallidum DNA a 275-bp fragment of the corresponding gene. The
complete nucleotide sequence of the gene was determined from fragments
amplified by long-distance PCR. Primer extension verified the assigned
translational start of the open reading frame (ORF) and putative upstream
promoter elements. The ORF encoded a highly basic (pI 9.6) 26-kDa protein
which contained an N-terminal 25-amino-acid leader peptide terminated by a
signal peptidase I cleavage site. The mature protein contained seven
tandemly spaced copies (as well as an eighth incomplete copy) of a
leucine-rich repeat (LRR), a motif previously identified in a number of
prokaryotic and eukaryotic proteins. Accordingly, the polypeptide was
designated T. pallidum leucine-rich repeat protein (TpLRR). Although Triton
X-114 phase partitioning showed that TpLRR was hydrophilic, cell
localization studies showed that most of the antigen was associated with
the peptidoglycan-cytoplasmic membrane complex rather than being freely
soluble in the periplasmic space. Immunoblot studies showed that syphilis
patients develop a weak antibody response to the antigen. Lastly, the
lrr(T. pallidum) gene was mapped to a 60-kb SfiI-SpeI fragment of the T.
pallidum chromosome which also contains the rrnA and flaA genes. The
function(s) of TpLRR is currently unknown; however, protein-protein and/or
protein-lipid interactions mediated by its LRR motifs may facilitate
interactions between components of the T. pallidum cell envelope.
Copyright © 1997, American Society for Microbiology
Molecular characterization and cellular localization of TpLRR, a processed leucine-rich repeat protein of Treponema pallidum, the syphilis spirochete
Department of Internal Medicine, U.T. Southwestern Medical Center at Dallas, Texas 75235, USA.
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