6MJT

Azurin 122F/124W/126Re

Summary for 6MJT

• Entry DOI: 10.2210/pdb6mjt/pdb
• Descriptor: Azurin, COPPER (II) ION, (1,10 PHENANTHROLINE)-(TRI-CARBON MONOXIDE) RHENIUM (I), ... (4 entities in total)
• Functional Keywords: electron hopping, electron transport
• Biological source: Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)
• Total number of polymer chains: 2
• Total formula weight: 29125.86

Authors

Takematsu, K.,Zalis, S.,Gray, H.B.,Vlcek, A.,Winkler, J.R.,Williamson, H.,Kaiser, J.T.,Heyda, J.,Hollas, D. (deposition date: 2018-09-21, release date: 2019-02-20, Last modification date: 2023-10-11)

Primary citation

Takematsu, K.,Williamson, H.R.,Nikolovski, P.,Kaiser, J.T.,Sheng, Y.,Pospisil, P.,Towrie, M.,Heyda, J.,Hollas, D.,Zalis, S.,Gray, H.B.,Vlcek, A.,Winkler, J.R.
Two Tryptophans Are Better Than One in Accelerating Electron Flow through a Protein.
ACS Cent Sci, 5:192-200, 2019

PubMed Abstract: We have constructed and structurally characterized a azurin mutant , where two adjacent tryptophan residues (W124 and W122, indole separation 3.6-4.1 Å) are inserted between the Cu center and a Re photosensitizer coordinated to the imidazole of H126 (Re(H126)(CO)(4,7-dimethyl-1,10-phenanthroline)). Cu oxidation by the photoexcited Re label (*Re) 22.9 Å away proceeds with a ∼70 ns time constant, similar to that of a single-tryptophan mutant (∼40 ns) with a 19.4 Å Re-Cu distance. Time-resolved spectroscopy (luminescence, visible and IR absorption) revealed two rapid reversible electron transfer steps, W124 → *Re (400-475 ps, ≅ 3.5-4) and W122 → W124 (7-9 ns, ≅ 0.55-0.75), followed by a rate-determining (70-90 ns) Cu oxidation by W122 ca. 11 Å away. The photocycle is completed by 120 μs recombination. No photochemical Cu oxidation was observed in , whereas in , the photocycle is restricted to the ReH126W124 unit and Cu remains isolated. QM/MM/MD simulations of 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 ∼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.

PubMed: 30693338
DOI: 10.1021/acscentsci.8b00882

Experimental method

X-RAY DIFFRACTION (1.893 Å)