title: Positive selection in tick saliva proteins of the Salp15 family.
abstract: When taking their blood meal on the mammalian host, ticks transfer a multitude of different proteins from their saliva into the host. Some of these proteins are hijacked by pathogens for their own purposes. Borrelia burgdorferi, the Lyme disease agent, is critically dependent on the presence of the tick protein Salp15 when infecting the host. Similarly, Anaplasma phagocytophilum, which causes anaplasmosis, needs Salp16, a homologue of Salp15, to get transferred from the host into the tick. Here we analyzed whether adaptive evolution has shaped the Salp15 protein family. Using site-specific estimates of K(A)/K(S) ratios, we identified different positions within the Salp15 protein family which have undergone a phase of positive selection. Additionally, we analyzed the B. burgdorferi protein interacting with Salp15, OspC. Again, sites showing signs of positive selection were identified, although they are more likely a result of the antigenic features of OspC than of the influence of Salp15. The identification of probably functionally relevant sites in the Salp15 family might direct the detailed experimental analysis of their interaction with human and bacterial proteins.
authors.affiliation: Department of Bioinformatics, Biocenter, University of Würzburg, Wurzburg, Germany.
authors.forename: Petra Catalina
authors.initials: PC
authors.lastname: Schwalie
authors.forename: Jörg
authors.initials: J
authors.lastname: Schultz
mesh_terms: D000220:Adaptation, Biological; D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics*; D001482:Base Composition; D025065:Borrelia burgdorferi / Q000235:genetics; D018884:Ixodes / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D055503:Protein Multimerization; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000235:genetics*; D012641:Selection, Genetic; D016415:Sequence Alignment
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; C079616:OspC protein; D012471:Salivary Proteins and Peptides; C464566:Salp15 protein, Ixodes scapularis