title: FhCaBP4: a Fasciola hepatica calcium-binding protein with EF-hand and dynein light chain domains.
abstract: In trematodes, there is a family of proteins which combine EF-hand-containing domains with dynein light chain (DLC)-like domains. A member of this family from the liver fluke, Fasciola hepatica-FhCaBP4-has been identified and characterised biochemically. FhCaBP4 has an N-terminal domain containing two imperfect EF-hand sequences and a C-terminal dynein light chain-like domain. Molecular modelling predicted that the two domains are joined by a flexible linker. Native gel electrophoresis demonstrated that FhCaBP4 binds to calcium, manganese, barium and strontium ions, but not to magnesium or zinc ions. The hydrophobic, fluorescent probe 8-anilinonaphthalene-1-sulphonate bound more tightly to FhCaBP4 in the presence of calcium ions. This suggests that the protein undergoes a conformational change on ion binding which increases the number of non-polar residues on the surface. FhCaBP4 was protected from limited proteolysis by the calmodulin antagonist W7, but not by trifluoperazine or praziquantel. Protein-protein cross-linking experiments showed that FhCaBP4 underwent calcium ion-dependent dimerisation. Since DLCs are commonly dimeric, it is likely that FhCaBP4 dimerises through this domain. The molecular model reveals that the calcium ion-binding site is located close to a key sequence in the DLC-like domain, suggesting a plausible mechanism for calcium-dependent dimerisation.
authors: Medical Biology Centre, School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors: Rebecca
authors: R
authors: Orr
authors: Ruth
authors: R
authors: Kinkead
authors: Richard
authors: R
authors: Newman
authors: Lindsay
authors: L
authors: Anderson
authors: Elizabeth M
authors: EM
authors: Hoey
authors: Alan
authors: A
authors: Trudgett
authors: David J
authors: DJ
authors: Timson
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics*; D004398:Dyneins / Q000235:genetics; D020832:EF Hand Motifs / Q000235:genetics; D005210:Fasciola hepatica / Q000235:genetics* / Q000378:metabolism*; D008670:Metals / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA
chemical_list: D002135:Calcium-Binding Proteins; D008670:Metals; D004398:Dyneins