{"database":"biostudies-other","file_versions":[],"scores":null,"additional":{"omics_type":["Unknown"],"volume":["85(3)"],"submitter":["Sillen A"],"journal":["Biophysical journal"],"pagination":["1882-93"],"full_dataset_link":["https://www.ebi.ac.uk/biostudies/studies/S-EPMC1303360"],"abstract":["The calcium-binding protein isolated from the sarcoplasm of the muscles of the sand worm Nereis diversicolor has four EF-hands and three active binding sites for Ca(2+) or Mg(2+). Nereis diversicolor sarcoplasmic calcium-binding protein contains three tryptophan residues at positions 4, 57, and 170, respectively. The Wt protein shows a very limited fluorescence increase upon binding of Ca(2+) or Mg(2+). Single-tryptophan-containing mutants were produced and purified. The fluorescence titrations of these mutants show a limited decrease of the affinity for calcium, but no alterations of the cooperativity. Upon adding calcium, Trp170 shows a strong fluorescence increase, Trp57 an extensive fluorescence decrease, and Trp4 shows no fluorescence change. Therefore mutant W4F/W170F is ideally suited to analyze the fluorescence titrations and to study the binding mechanism. Mutations of the calcium ligands at the z-position in the three binding sites show no effect at site I and a total loss of cooperativity at sites III and IV. The quenching of Trp57 upon calcium binding is dependent on the presence of arginine R25, but this residue is not just a simple dynamic quencher. The role of the salt bridge R25-D58 is also investigated."],"repository":["biostudies-other"],"pmcid":["PMC1303360"],"data_source":["Europe PMC"],"pubmed_authors":["Robben J","Verheyden S","Engelborghs Y","Braem T","Sillen A","Volckaert G","Delfosse L"],"additional_accession":[]},"is_claimable":false,"name":"Mechanism of fluorescence and conformational changes of the sarcoplasmic calcium binding protein of the sand worm Nereis diversicolor upon Ca2+ or Mg2+ binding.","description":"The calcium-binding protein isolated from the sarcoplasm of the muscles of the sand worm Nereis diversicolor has four EF-hands and three active binding sites for Ca(2+) or Mg(2+). Nereis diversicolor sarcoplasmic calcium-binding protein contains three tryptophan residues at positions 4, 57, and 170, respectively. The Wt protein shows a very limited fluorescence increase upon binding of Ca(2+) or Mg(2+). Single-tryptophan-containing mutants were produced and purified. The fluorescence titrations of these mutants show a limited decrease of the affinity for calcium, but no alterations of the cooperativity. Upon adding calcium, Trp170 shows a strong fluorescence increase, Trp57 an extensive fluorescence decrease, and Trp4 shows no fluorescence change. Therefore mutant W4F/W170F is ideally suited to analyze the fluorescence titrations and to study the binding mechanism. Mutations of the calcium ligands at the z-position in the three binding sites show no effect at site I and a total loss of cooperativity at sites III and IV. The quenching of Trp57 upon calcium binding is dependent on the presence of arginine R25, but this residue is not just a simple dynamic quencher. The role of the salt bridge R25-D58 is also investigated.","dates":{"release":"2003-01-01T00:00:00Z","publication":"2003 Sep","modification":"2019-03-26T22:29:02Z","creation":"2019-03-26T22:29:02Z"},"accession":"S-EPMC1303360","cross_references":{"pubmed":["12944301"],"doi":["10.1016/S0006-3495(03)74616-5 "],"pdb":["12pt","69pt"]}}