Molecular and expression analysis of a family of the Amblyomma americanum tick Lospins.
Serine proteinase inhibitors (serpins) are a family of structurally similar but functionally diverse proteins that regulate several important proteolytic cascades in most branches of life. We have characterized 17 Amblyomma americanum serpin cDNAs here named as ;Lospins' (L; an acronym for Lone Star tick serpin) that possess three beta-sheets, eight alpha-helices and a reactive center loop consistent with the consensus serpin superfamily secondary structures. Visual inspection of deduced amino acid sequences revealed two patterns of basic residues: (i) (86)DKSRVLKAYKRL(97) in L5 and L13-16 and (ii) (158)VRDKTRGKI(166) in all Lospins, which are similar to consensus glycosaminoglycan (GAG) binding sites (XBnXmBX, where X and B are non-basic and basic residues, n=1 or 2 and m=1, 2 or 3). On three-dimensional models, the two putative GAG binding sites mapped onto alpha-helices D and F, respectively, with calculation of electrostatic surface potentials revealing basic patches on L5 and L13-16 models that are comparable to the heparin-binding site on antithrombin. RT-PCR expression analysis of 15 selected genes showed that the majority (11/15) of the Lospins were ubiquitously expressed in the midgut, ovary and salivary glands. On a neighbor-joining phylogeny guide tree, 15 serpins from other ticks and 17 Lospins from this study, a total of 32 tick serpin sequences, segregated into five groups with Lospins in groups A and D being conserved across tick species. The discovery of Lospins in this study sets the framework for future studies to understand the role of serpins in tick physiology.
Mulenga
Albert
A
Department of Entomology, College of Agriculture and Life Sciences, Texas A & M University, TAMU 2475, College Station, TX 77843, USA. a-mulenga@tamu.edu
Khumthong
Rabuesak
R
Blandon
Maria A
MA
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D026863:Ixodidae / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D012313:RNA / Q000235:genetics; D015843:Serpins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D015843:Serpins; D012313:RNA