title: Cloning and sequencing of putative calreticulin complementary DNAs from four hard tick species.
abstract: Calreticulin (CRT) is a calcium-binding protein and has many functions in eukaryotic cells. CRT is possibly involved in parasite host immune system evasion. To better understand the molecular basis of CRT in ticks, we cloned and sequenced 4 full-length complementary DNAs (cDNAs) from the hard tick species, Dermacentor variabilis, Haemaphysalis longicornis, Ixodes scapularis, and Rhipicephalus sanguineus, using the technique of rapid amplification of cDNA ends. The deduced amino acid sequences share high identities (between 77 and 98%) with 3 known tick CRT sequences. The major characteristics of known CRTs are observed in all 4 of our deduced tick CRTs. These include 3 major domains, a signal peptide sequence at the beginning of the coding region, 2 triplets of conserved regions, cysteine sites providing disulfide bridges for N-terminal folding, and a nuclear localization signal. Remarkably, the replacement of the endoplasmic reticulum retention signal KDEL by HEEL, which is believed to be associated with secretion of CRT into the host during feeding and was previously recorded only in 2 ticks and a hookworm, is also present in all 4 of our tick putative CRTs. In addition, the CRT gene is potentially useful for tick phylogenetic reconstruction.
authors.affiliation: Department of Biology and Institute of Arthropodology and Parasitology, Georgia Southern University, Statesboro, Georgia 30460-8042, USA.
authors.forename: Guang
authors.initials: G
authors.lastname: Xu
authors.forename: Quentin Q
authors.initials: QQ
authors.lastname: Fang
authors.forename: James E
authors.initials: JE
authors.lastname: Keirans
authors.forename: Lance A
authors.initials: LA
authors.lastname: Durden
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D037282:Calreticulin / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000737:chemistry*; D003870:Dermacentor / Q000737:chemistry / Q000145:classification / Q000235:genetics; D004285:Dogs; D005786:Gene Expression Regulation; D018884:Ixodes / Q000737:chemistry / Q000145:classification / Q000235:genetics; D026863:Ixodidae / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D021382:Protein Sorting Signals / Q000235:genetics; D019105:Random Amplified Polymorphic DNA Technique; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D037282:Calreticulin; D018076:DNA, Complementary; D021382:Protein Sorting Signals; D003545:Cysteine