ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Thespectroscopic properties of Trp152 of eel skeletal muscletroponin C have been studied under conditions in which the COOH-domain is depleted of metal ions, titrated with Mg2+ andsubsequently with Ca2+. This spectroscopic study clearly showsthat the Mg2+ or Ca2+-bound states substitution lead to distinctconformations of the COOH-domain. The analysis of eel troponin Cabsorption and Trp152 fluorescence emission spectra indicates amore polar environment in the Mg2+-bound state of the protein.Steady state tryptophan polarization and lifetime distributiondata indicate that the motion of the indole moiety is morerestricted in the Mg2+ state of the protein than in the Ca2+-bound state. However, fluorescence quenching data using I−and Cs+ show that Trp152 is more accessible to the solvent in theMg2+-bound state of eel troponin C. This spectroscopic analysisof the distinct Ca2+ and Mg2+-bound states of eel troponin C isconsistent with the description of the three-dimensionalstructure of the corresponding states of pike (pI = 4.10)parvalbumin which is structurally homologous to the COOH-domainof troponin C. Since it appears that during muscular contraction,magnesium ions, which occupy the binding sites of the COOH-domainof troponin C in the resting cell are replaced by calcium ions,the structural shift occurring upon Mg2+/Ca2+ substitution, musthave a physiological significance. The role of this domain isprobably not limited to a structural role
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018622109391
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