Internal electron transfer and structural dynamics of cd1 nitrite reductase revealed by laser CO photodissociation

Biochemistry
E K WilsonP Brzezinski

Abstract

Laser photolysis techniques have been employed to investigate the internal electron transfer (eT) reaction within Pseudomonas aeruginosa nitrite reductase (Pa-NiR). We have measured the (d1--> c) internal eT rate for the wild-type protein and a site-directed mutant (Pa-NiR H327A) which has a substitution in the d1-heme binding pocket; we found the rate of eT to be fast, keT = 2.5 x 10(4) and 3.5 x 10(4) s-1 for the wild-type and mutant Pa-NiR, respectively. We also investigated the photodissociation of CO from the fully reduced proteins and observed microsecond first-order relaxations; these imply that upon breakage of the Fe2+-CO bond, both Pa-NiR and Pa-NiR H327A populate a nonequilibrium state which decays to the ground state with a complex time course that may be described by two exponential processes (k1 = 3 x 10(4) s-1 and k2 = 0.25 x 10(4) s-1). These relaxations do not have a kinetic difference spectrum characteristic of CO recombination, and therefore we conclude that Pa-NiR undergoes structural rearrangements upon dissociation of CO. The bimolecular rate of CO rebinding is 5 times faster in Pa-NiR H327A than in the wild-type enzyme (1.1 x 10(5) M-1 s-1 compared to 2 x 10(4) M-1 s-1), indicating that this mutation in t...Continue Reading

References

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Citations

May 30, 2009·The Journal of Biological Chemistry·Agnès de Lacroix de LavaletteFrancesca Zito
Feb 28, 2001·Proceedings of the National Academy of Sciences of the United States of America·F CutruzzolaM Brunori
Sep 21, 2001·Journal of Molecular Biology·K BrownM Tegoni
Jun 1, 2001·Methods : a Companion to Methods in Enzymology·A BellelliM T Wilson
Aug 7, 2001·The Journal of Biological Chemistry·A ArcovitoA Bellelli
Jun 9, 2005·Chemical Reviews·Konrad SzaciłowskiGrazyna Stochel
Feb 12, 2011·Journal of the American Chemical Society·Marina RadoulDaniella Goldfarb

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