title: FhCaBP3: a Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains.
abstract: A DNA sequence encoding a protein with predicted EF-hand and dynein light chain binding domains was identified in a Fasciola hepatica EST library. Sequence analysis of the encoded protein revealed that the most similar known protein was the Fasciola gigantica protein FgCaBP3 and so this newly identified protein was named FhCaBP3. Molecular modelling of FhCaBP3 predicted a highly flexible N-terminal region, followed by a domain containing two EF-hand motifs the second of which is likely to be a functioning divalent ion binding site. The C-terminal domain of the protein contains a dynein light chain like region. Interestingly, molecular modelling predicts that calcium ion binding to the N-terminal domain destabilises the β-sheet structure of the C-terminal domain. FhCaBP3 can be expressed in, and purified from, Escherichia coli. The recombinant protein dimerises and the absence of calcium ions appeared to promote dimerisation. Native gel shift assays demonstrated that the protein bound to calcium and manganese ions, but not to magnesium, barium, zinc, strontium, nickel, copper or cadmium ions. FhCaBP3 interacted with the calmodulin antagonists trifluoperazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and chlorpromazine as well as the myosin regulatory light chain-binding drug praziquantel. Despite sequence and structural similarities to other members of the same protein family from F. hepatica, FhCaBP3 has different biochemical properties to the other well characterised family members, FH22 and FhCaBP4. This suggests that each member of this trematode calcium-binding family has discrete functional roles within the organism.
authors.affiliation: School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, UK.
authors.forename: Samantha
authors.initials: S
authors.lastname: Banford
authors.forename: Orla
authors.initials: O
authors.lastname: Drysdale
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Hoey
authors.forename: Alan
authors.initials: A
authors.lastname: Trudgett
authors.forename: David J
authors.initials: DJ
authors.lastname: Timson
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004398:Dyneins / Q000737:chemistry*; D005210:Fasciola hepatica; D015801:Helminth Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017421:Sequence Analysis
chemical_list: D002135:Calcium-Binding Proteins; D015801:Helminth Proteins; D004398:Dyneins; D002118:Calcium