The role of His117 in the redox reactions of azurin from Pseudomonas aeruginosa.
The electron-transfer properties of H117G- and wild-type azurin were compared by applying both as electron acceptors in the conversion of 4-ethylphenol by 4-ethylphenol methylenehydroxylase (4-EPMH). The reactivity of H117G-azurin was determined in the absence and presence of imidazoles, which can substitute the missing fourth ligand. In the absence of imidazoles, H117G-azurin reacted directly with 4-ethylphenol; this reaction was abolished in the presence of imidazoles. The enzymatic reduction of H117G-azurin by 4-EPMH was 40 times slower than that of wild-type azurin. The rate of this reaction was enhanced by some imidazoles, diminished by others. In all cases the reduction of H117G-azurin was irreversible. These results demonstrate that His117 is vital for electron transfer and effectively protects the copper site against aspecific reactions.
Gorren
A C
AC
Department of Microbiology and Enzymology, Delft University of Technology, The Netherlands.
den Blaauwen
T
T
Canters
G W
GW
Hopper
D J
DJ
Duine
J A
JA
D001400:Azurin / Q000737:chemistry* / Q000378:metabolism*; D004579:Electron Transport; D006639:Histidine; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D010084:Oxidation-Reduction; D017354:Point Mutation; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D013053:Spectrophotometry
D007093:Imidazoles; D001400:Azurin; D006639:Histidine