Ca2+-dependent conformational changes in the neuronal Ca2+-sensor recoverin probed by the fluorescent dye Alexa647статья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.

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[1] Ca2+-dependent conformational changes in the neuronal ca2+-sensor recoverin probed by the fluorescent dye alexa647 / G. Thomas, K. E. Komolov, I. I. Senin et al. // Proteins: Structure, Function and Bioinformatics. — 2007. — Vol. 66, no. 2. — P. 492–499. Abstract Recoverin belongs to the superfamily of EF-hand Ca2+-binding proteins and operates as a Ca2+-sensor in vertebrate photoreceptor cells, where it regulates the activity of rhodopsin kinase GRK1 in a Ca2+-dependent manner. Ca2+-dependent conformational changes in recoverin are allosterically controlled by the covalently attached myristoyl group. The amino acid sequence of recoverin harbors a unique cysteine at position 38. The cysteine can be modified by the fluorescent dye Alexa647 using a maleimide-thiol coupling step. Introduction of Alexa647 into recoverin did not disturb the biological function of recoverin, as it can regulate rhodopsin kinase activity like unlabeled recoverin. Performance of the Ca2+-myristoyl switch of labeled recoverin was monitored by Ca2+-dependent association with immobilized lipids using surface plasmon resonance spectroscopy. When the Ca2+-concentration was varied, labeled myristoylated recoverin showed a 37%-change in fluorescence emission and a 34%-change in excitation intensity, emission and excitation maxima shifted by 6 and 18 nm, respectively. In contrast, labeled nonmyristoylated recoverin exhibited only minimal changes. Time-resolved fluorescence measurements showed biexponentiell fluorescence decay, in which the slower time constant of 2 ns was specifically influenced by Ca2+-induced conformational changes. A similar influence on the slower time constant was observed with the recoverin mutant RecE85Q that has a disabled EF-hand 2, but no such influence was detected with the mutant RecE121Q (EF-hand 3 is nonfunctional) that contains the myristoyl group in a clamped position. We conclude from our results that Alexa647 bound to cysteine 38 can monitor the conformational transition in recoverin that is under control of the myristoyl group. [ DOI ]

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