Complex kinetics of the electron transfer between the photoactive redox label TUPS and the heme of cytochrome c.
The photoinduced covalent redox label 8-thiouredopyrene-1,3,6-trisulfonate (TUPS) has been attached to two lysine residues (K8 and K39) at opposite sides of horse heart cytochrome c, as well as to cysteines, at the same positions, introduced by site-directed mutagenesis. Electron transfer between TUPS and the heme of cytochrome c deviates from the expected monoexponential kinetic behavior. Neither the overall rate nor the individual exponential components of electron transfer, as followed by kinetic absorption spectroscopy, correlate with the length of the covalent link connecting the dye with the protein. Molecular dynamics calculations show that TUPS can approach the protein surface and occupy several such positions. This heterogeneity may explain the multiexponential electron-transfer kinetics. The calculated optimal electron-transfer pathways do not follow the covalent link but involve through space jumps from the dye to the protein moiety, effectively decoupling the length of the covalent link and the electron-transfer rates.
Tenger
Katalin
K
Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, Hungary.
Khoroshyy
Petro
P
Leitgeb
Balázs
B
Rákhely
Gábor
G
Borovok
Natalia
N
Kotlyar
Alexander
A
Dolgikh
Dmitry A
DA
Zimányi
László
L
D003545:Cysteine / Q000737:chemistry; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics; D004579:Electron Transport / Q000502:physiology*; D019277:Entropy; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D011721:Pyrenes / Q000737:chemistry*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D013054:Spectrophotometry, Atomic; D013499:Surface Properties
D011721:Pyrenes; D011994:Recombinant Proteins; C121436:thiouredopyrenetrisulfonate; D006418:Heme; D045304:Cytochromes c; D008239:Lysine; D003545:Cysteine