Structure of a de novo designed protein model of radical enzymes.
The use of side chains as catalytic cofactors for protein mediated redox chemistry raises significant mechanistic issues as to how these amino acids are activated toward radical chemistry in a controlled manner. De novo protein design has been used to examine the structural basis for the creation and maintenance of a tryptophanyl radical in a three-helix bundle protein maquette. Here we report the detailed structural analysis of the protein by multidimensional NMR methods. An interesting feature of the structure is an apparent pi-cation interaction involving the sole tryptophan and a lysine side chain. Hybrid density functional calculations support the notion that this interaction raises the reduction potential of the W degrees /WH redox pair and helps explain the redox characteristics of the protein. This model protein system therefore provides a powerful model for exploring the structural basis for controlled radical chemistry in protein.
Dai
Qing-Hong
QH
The Johnson Research Foundation and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6059, USA.
Tommos
Cecilia
C
Fuentes
Ernesto J
EJ
Blomberg
Margareta R A
MR
Dutton
P Leslie
PL
Wand
A Joshua
AJ
D004798:Enzymes / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*
D004798:Enzymes; D011506:Proteins; D008239:Lysine