title: Analysis of the role of Mg²⁺ on conformational change and target recognition by ciliate Euplotes octocarinatus centrin.
abstract: The binding of Mg(2+) with the Euplotes octocarinatus centrin (EoCen) and the effect of Mg(2+) on the binding of EoCen with the peptide melittin were examined by spectroscopic methods. In this study, it was found that Mg(2+) may bind with Ca(2+)-binding sites, at least partly, on EoCen, which displays ∼10-fold weaker affinity than Ca(2+). In the presence of Mg(2+), Ca(2+)-saturated EoCen undergoes significant conformational changes resulting in decreased exposure of hydrophobic surfaces on the protein. Additionally, excess Mg(2+) did not change the stoichiometry, but rather reduced the affinity of EoCen to melittin. The Mg(2+)-dependent decrease in the affinities of EoCen to melittin is an intrinsic property of Mg(2+), rather than a nonspecific ionic effect. The inhibitory effect of Mg(2+) on the formation of complexes between EoCen and melittin may contribute to the specificity of EoCen in target activation in response to cellular Ca(2+) concentration fluctuations.
authors.affiliation: Institute of Biotechnology, Shanxi University, Taiyuan 030006, China.
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.forename: Yanan
authors.initials: Y
authors.lastname: Feng
authors.forename: Aihua
authors.initials: A
authors.lastname: Liang
authors.forename: Binsheng
authors.initials: B
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry; D002942:Circular Dichroism; D016812:Euplotes / Q000378:metabolism*; D007477:Ions / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry* / Q000502:physiology; D008555:Melitten / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007477:Ions; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D008555:Melitten; D008274:Magnesium; D002118:Calcium