Tryptophan-accelerated electron flow through proteins.
Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. Cu(I) oxidation by a photoexcited Re(I)-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) beta strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.
Shih
Crystal
C
Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
Museth
Anna Katrine
AK
Abrahamsson
Malin
M
Blanco-Rodriguez
Ana Maria
AM
Di Bilio
Angel J
AJ
Sudhamsu
Jawahar
J
Crane
Brian R
BR
Ronayne
Kate L
KL
Towrie
Mike
M
Vlcek
Antonín
A
Richards
John H
JH
Winkler
Jay R
JR
Gray
Harry B
HB
D001400:Azurin / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D004735:Energy Transfer; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D050505:Mutant Proteins / Q000737:chemistry; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry; D013057:Spectrum Analysis; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry
D008024:Ligands; D050505:Mutant Proteins; D001400:Azurin; D014443:Tyrosine; D010649:Phenylalanine; D012211:Rhenium; D003300:Copper; D014364:Tryptophan