title: Purification and characterization of Campylobacter rectus surface layer proteins.
abstract: Campylobacter rectus is a putative periodontopathogen which expresses a proteinaceous surface layer (S-layer) external to the outer membrane. S-layers are considered to play a protective role for the microorganism in hostile environments. The S-layer proteins from six different C. rectus strains (five human isolates and a nonhuman primate [NHP] isolate) were isolated, purified, and characterized. The S-layer proteins of these strains varied in molecular mass (ca. 150 to 166 kDa) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They all reacted with monospecific rabbit antiserum to the purified S-layer of C. rectus 314, but a quantitative enzyme-linked immunosorbent assay demonstrated a strong antigenic relationship among the five human strains, while the NHP strain, 6250, showed weaker reactivity. Amino acid composition analysis showed that the S-layers of four C. rectus strains contained large proportions of acidic amino acids (13 to 27%) and that >34% of the amino acid residues were hydrophobic. Amino acid sequence analysis of six S-layer proteins revealed that the first 15 amino-terminal amino acids were identical and showed seven residues of identity with the amino-terminal sequence of the Campylobacter fetus S-layer protein SapA1. CNBr peptide profiles of the S-layer proteins from C. rectus 314, ATCC 33238, and 6250 confirmed that the S-layer proteins from the human strains were similar to each other and somewhat different from that of the NHP isolate (strain 6250). However, the S-layer proteins from the two human isolates do show some structural heterogeneity. For example, there was a 17-kDa fragment unique to the C. rectus 314 S-layer. The amino-terminal sequence of this peptide had homology with the C. rectus 51-kDa porin and was composed of nearly 50% hydrophobic residues. Thus, the S-layer protein from C. rectus has structural heterogeneity among different human strains and immunoheterogeneity with the NHP strain.
authors.affiliation: Department of Periodontics, University of Texas Health Science Center at San Antonio, 78284, USA.
authors.forename: H
authors.initials: H
authors.lastname: Nitta
authors.forename: S C
authors.initials: SC
authors.lastname: Holt
authors.forename: J L
authors.initials: JL
authors.lastname: Ebersole
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification*; D001426:Bacterial Proteins; D002167:Campylobacter / Q000737:chemistry* / Q000302:isolation & purification; D003488:Cyanogen Bromide; D006801:Humans; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D013045:Species Specificity
chemical_list: D000596:Amino Acids; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; C055764:S-layer proteins; D003488:Cyanogen Bromide