title: Molecular characterization and cellular localization of TpLRR, a processed leucine-rich repeat protein of Treponema pallidum, the syphilis spirochete.
abstract: 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.
authors.affiliation: Department of Internal Medicine, U.T. Southwestern Medical Center at Dallas, Texas 75235, USA.
authors.forename: D V
authors.initials: DV
authors.lastname: Shevchenko
authors.forename: D R
authors.initials: DR
authors.lastname: Akins
authors.forename: E
authors.initials: E
authors.lastname: Robinson
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: T G
authors.initials: TG
authors.lastname: Popova
authors.forename: D L
authors.initials: DL
authors.lastname: Cox
authors.forename: J D
authors.initials: JD
authors.lastname: Radolf
mesh_terms: D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification*; D001483:Base Sequence; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics; D002874:Chromosome Mapping; D003593:Cytoplasm / Q000737:chemistry; D007930:Leucine / Q000378:metabolism*; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000737:chemistry; D017433:Protein Structure, Secondary; D012091:Repetitive Sequences, Nucleic Acid; D013587:Syphilis / Q000382:microbiology*; D014210:Treponema pallidum / Q000737:chemistry* / Q000235:genetics*
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D010457:Peptidoglycan; C105994:TpLRR protein, Treponema pallidum; D007930:Leucine