Resolution of two distinct electron transfer sites on azurin
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Resolution of two distinct electron transfer sites on azurin. / Farver, O; Blatt, Y; Pecht, I.
In: Biochemistry, Vol. 21, No. 15, 20.07.1982, p. 3556-61.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Resolution of two distinct electron transfer sites on azurin
AU - Farver, O
AU - Blatt, Y
AU - Pecht, I
PY - 1982/7/20
Y1 - 1982/7/20
N2 - Pseudomonas aeruginosa azurin is stoichiometrically and specifically labeled upon reduction by Cr(II)aq ions, yielding a substitution-inert Cr(III) adduct on the protein surface. We investigated the effect of this chemical modification on the reactivity of azurin with two of its presumed partners in the redox system of the bacterium. The Pseudomonas cytochrome oxidase catalyzed oxidation of reduced native and Cr(III)-labeled azurin by O2 was found to be unaffected by the modification. The kinetics of the electron exchange reaction between native or Cr(III)-labeled azurin and cytochrome c551 were studied by the temperature-jump method. Though similar chemical relaxation spectra were observed for native and modified systems, they differ quantitatively. Analysis of the concentration dependences of the relaxation times and amplitudes showed that both obey the same mechanism but that the specific reaction rates of the Cr(III)-modified protein are attenuated. This decreased reactivity of Cr(III)-labeled azurin toward one of its physiological partners suggests the involvement of the labeled region in the electron transfer reaction with cytochrome c551. Furthermore, the presence of a second active site, involved in the reduction of cytochrome oxidase, is suggested by the results.
AB - Pseudomonas aeruginosa azurin is stoichiometrically and specifically labeled upon reduction by Cr(II)aq ions, yielding a substitution-inert Cr(III) adduct on the protein surface. We investigated the effect of this chemical modification on the reactivity of azurin with two of its presumed partners in the redox system of the bacterium. The Pseudomonas cytochrome oxidase catalyzed oxidation of reduced native and Cr(III)-labeled azurin by O2 was found to be unaffected by the modification. The kinetics of the electron exchange reaction between native or Cr(III)-labeled azurin and cytochrome c551 were studied by the temperature-jump method. Though similar chemical relaxation spectra were observed for native and modified systems, they differ quantitatively. Analysis of the concentration dependences of the relaxation times and amplitudes showed that both obey the same mechanism but that the specific reaction rates of the Cr(III)-modified protein are attenuated. This decreased reactivity of Cr(III)-labeled azurin toward one of its physiological partners suggests the involvement of the labeled region in the electron transfer reaction with cytochrome c551. Furthermore, the presence of a second active site, involved in the reduction of cytochrome oxidase, is suggested by the results.
KW - Azurin
KW - Bacterial Proteins
KW - Chromium
KW - Kinetics
KW - Oxidation-Reduction
KW - Pseudomonas aeruginosa
KW - Temperature
M3 - Journal article
C2 - 6810925
VL - 21
SP - 3556
EP - 3561
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 15
ER -
ID: 113627011