title: Spectral study on the binding of gadolinium ions with apoovotransferrin.
abstract: The binding of Gd3+ ion to apoovotransferrin (apoOTf) was monitored by means of UV difference spectra in 0.01M Hepes, pH 7.4 at 25 degrees C. Used 2-p-toluidinylnaphthalene-6-sulfonate (TNS) as fluorescence probe the conformational changes of protein were studied while gadolinium ions bound to apoOTf. The results show that Gd3+ binding produces peaks at 244 and 294 nm that is the characteristic of binding at the apoOTf specific metal-binding sites. At 244 nm the molar absorptivity of Gd-apoOTf complex is (1.99+/-0.17)x10(4)cm(-1)M(-1). The apparent binding constants for the complexes of Gd3+ with apoovotransferrin are logK(1)=7.61+/-0.14 and logK(2)=4.96+/-0.26. A very large conformational change of apoovotransferrin appears when Gd3+ is bound to the N-terminal binding site. When Gd3+ is bound to C-terminal binding site there is less conformational change.
authors.affiliation: Key Laboratory of Chemical Biology and Molecular Engineering of Ministry of Education, Institute of Molecular Science, Shanxi University, Taiyuan 030006, China.
authors.forename: Jin-Ling
authors.initials: JL
authors.lastname: Wang
authors.forename: Ying-Qi
authors.initials: YQ
authors.lastname: Li
authors.forename: Bin-Sheng
authors.initials: BS
authors.lastname: Yang
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002021:Buffers; D002645:Chickens; D005456:Fluorescent Dyes / Q000378:metabolism; D005682:Gadolinium / Q000737:chemistry* / Q000378:metabolism; D006531:HEPES / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D009282:Naphthalenesulfonates / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013816:Thermodynamics; D014168:Transferrin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001059:Apoproteins; D002021:Buffers; D005456:Fluorescent Dyes; D007477:Ions; D009282:Naphthalenesulfonates; D014168:Transferrin; C028284:apotransferrin; C009497:2-(4-toluidino)-6-naphthalenesulfonic acid; D005682:Gadolinium; D006531:HEPES