title: A tyrosine-tryptophan dyad and radical-based charge transfer in a ribonucleotide reductase-inspired maquette.
abstract: In class 1a ribonucleotide reductase (RNR), a substrate-based radical is generated in the α2 subunit by long-distance electron transfer involving an essential tyrosyl radical (Y122O·) in the β2 subunit. The conserved W48 β2 is ∼10 Å from Y122OH; mutations at W48 inactivate RNR. Here, we design a beta hairpin peptide, which contains such an interacting tyrosine-tryptophan dyad. The NMR structure of the peptide establishes that there is no direct hydrogen bond between the phenol and the indole rings. However, electronic coupling between the tyrosine and tryptophan occurs in the peptide. In addition, downshifted ultraviolet resonance Raman (UVRR) frequencies are observed for the radical state, reproducing spectral downshifts observed for β2. The frequency downshifts of the ring and CO bands are consistent with charge transfer from YO· to W or another residue. Such a charge transfer mechanism implies a role for the β2 Y-W dyad in electron transfer.
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Cynthia V
authors.initials: CV
authors.lastname: Pagba
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Tyler G
authors.initials: TG
authors.lastname: McCaslin
authors.affiliation: Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, USA.|Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Veglia
authors.affiliation: Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, USA.|Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.|Department for Innovation in Biological, Agro-food and Forest Systems, University of Tuscia, Viterbo 01100, Italy.
authors.forename: Fernando
authors.initials: F
authors.lastname: Porcelli
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Jiby
authors.initials: J
authors.lastname: Yohannan
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Zhanjun
authors.initials: Z
authors.lastname: Guo
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Miranda
authors.initials: M
authors.lastname: McDaniel
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Bridgette A
authors.initials: BA
authors.lastname: Barry
mesh_terms: D020816:Amino Acid Motifs; D004579:Electron Transport; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005095:Exoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006860:Hydrogen Bonding; D008958:Models, Molecular; D014364:Tryptophan / Q000737:chemistry* / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C489683:rnr protein, E coli; D014443:Tyrosine; D014364:Tryptophan; D005095:Exoribonucleases