Binding of lanthanide ions to troponin C

Autor:	John Gergely, W. Dew Horrocks, Paul C. Leavis, Chih-Lueh Albert Wang
Rok vydání:	1981
Předmět:	Lanthanide Chemistry Muscles Muscle Proteins Chromophore Biochemistry Fluorescence Troponin Troponin C Crystallography Spectrometry Fluorescence Europium Excited state Animals Tyrosine Molecule Rabbits Binding site Terbium Luminescence Mathematics Protein Binding
Zdroj:	Biochemistry. 20:2439-2444
ISSN:	1520-4995 0006-2960
DOI:	10.1021/bi00512a012
Popis:	Tb3+ and Eu3+ bound to troponin C were detected by (1) changes in the fluorescence of the tyrosine chromophore of the protein or (2) the luminescence of the ions themselves excited by energy transfer from the protein or by direct excitation using a pulsed laser light source [Horrocks, W. DeW., Jr., & Sudnick, D. R. (1979) Science (Washington, D.C.) 206, 1194-1196]. Titrations carried out in the absence and presence of Ca2+ suggest two classes of binding sites (two sites in each class) for the lanthanides, corresponding to the high- and the low-affinity sites for Ca2+. Computer analysis, assuming competition between Ca2+ and the lanthanide, using the binding constants of Ca2+ for TnC [Potter, J. D., & Gergely, J. (1975( J. Biol. Chem. 250, 4628-4633] yields 5.2 X 10(8) M-1 and 9.7 X 10(6) M-1 for Tb3+ and 4.7 X 10(9) M-1 and 5.3 X 10(7) M-1 for Eu3+, for the high- and the low-affinity sites, respectively. From lifetimes of laser-induced luminescence in H2O and in D2O, the number of water molecules coordinated to Eu3+ was two at the high and three at the low affinity sites.
Databáze:	OpenAIRE
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