Nanosecond fluorescence of tryptophans in cytochrome P-450scc (CYP11A1): effect of substrate binding. |
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Authors: | P Anzenbacher J Hudecek S Vajda V Fidler C Larroque R Lange |
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Affiliation: | Institute of Physiology, Czechoslovak Academy of Sciences, Prague. |
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Abstract: | Fluorescence of eight tryptophan residues in cytochrome P-450scc with bound endogenous cholesterol could be fitted with a two component model: a single exponential and a "top-hat" distribution of lifetimes as the second component. The short-lived component (tau 1 about 700 ps) does not change significantly upon binding of substrate (22R-hydroxycholesterol). The parameters of the long-lived component (central lifetime tau m about 3.4 ns) change upon binding of carbon monoxide and substrate. 22R-hydroxycholesterol binding broadens the distribution of the long-lived component; that is the heterogeneity of the Trp environment is increased when this substrate displaces the endogenous cholesterol. |
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