Two Tryptophans Are Better Than One in Accelerating Electron Flow through a Protein

0500238 - ÚFCH JH 2020 RIV US eng J - Článek v odborném periodiku
Takematsu, K. - Williamson, H. - Nikolovski, P. - Kaiser, J. T. - Sheng, Y. - Pospíšil, Petr - Towrie, M. - Heyda, J. - Hollas, D. - Záliš, Stanislav - Gray, H. B. - Vlček, Antonín - Winkler, J. R.
Two Tryptophans Are Better Than One in Accelerating Electron Flow through a Protein.
ACS Central Science. Roč. 5, č. 1 (2019), s. 192-200. ISSN 2374-7943. E-ISSN 2374-7951
Grant CEP: GA ČR GA17-01137S
Institucionální podpora: RVO:61388955
Klíčová slova: subunit interface * generation * excitation * dynamics
Obor OECD: Physical chemistry
Impakt faktor: 12.685, rok: 2019
Způsob publikování: Open access

We have constructed and structurally characterized a Pseudomonas aeruginosa azurin mutant Re126WWCu(I), where two adjacent tryptophan residues (W124 and W122, indole separation 3.6-4.1 angstrom) are inserted between the CuI center and a Re photosensitizer coordinated to the imidazole of H126 (Re-I(H126)-(CO)(3)(4,7-dimethyl-1,10-phenanthroline)(+)). Cu-I oxidation by the photoexcited Re label (*Re) 22.9 angstrom away proceeds with a similar to 70 ns time constant, similar to that of a single-tryptophan mutant (similar to 40 ns) with a 19.4 angstrom Re-Cu distance. Time-resolved spectroscopy (luminescence, visible and IR absorption) revealed two rapid reversible electron transfer steps, W124 -> *Re (400-475 ps, K-1 congruent to 3.5-4) and W122 -> W124(center dot+) (7-9 ns, K-2 congruent to 0.55-0.75), followed by a rate-determining (70-90 ns) Cu-I oxidation by W122(+) ca. 11 angstrom away. The photocycle is completed by 120 mu s recombination. No photochemical Cu-I oxidation was observed in Re126FWCu(I), whereas in Re126WFCu(I), the photocycle is restricted to the ReH126W124 unit and Cu-I remains isolated. QM/MM/MD simulations of Re126WWCu(I) indicate that indole solvation changes through the hopping process and W124 -> *Re electron transfer is accompanied by water fluctuations that tighten W124 solvation. Our finding that multistep tunneling (hopping) confers a similar to 9000-fold advantage over single-step tunneling in the double-tryptophan protein supports the proposal that hole-hopping through tryptophan/tyrosine chains protects enzymes from oxidative damage.
Trvalý link: http://hdl.handle.net/11104/0292342