Nanosecond fluorescence of tryptophans in cytochrome P-450scc (CYP11A1): effect of substrate binding.
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.
Anzenbacher
P
P
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
Hudecek
J
J
Vajda
S
S
Fidler
V
V
Larroque
C
C
Lange
R
R
D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002784:Cholesterol / Q000378:metabolism*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008961:Models, Structural; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence / Q000379:methods; D014364:Tryptophan
D014364:Tryptophan; D002784:Cholesterol; D002786:Cholesterol Side-Chain Cleavage Enzyme