Probing Heme Coordination States of Inducible Nitric Oxide Synthase with a Re(I)(imidazole-alkyl-nitroarginine) Sensitizer-Wire
Abstract
Mammalian inducible nitric oxide synthase (iNOS) catalyzes the production of L-citrulline and nitric oxide (NO) from L-arginine and O_2. The Soret peak in the spectrum of the iNOS heme domain (iNOS_(oxy)) shifts from 423 to 390 nm upon addition of a sensitizer-wire, [Re^I-imidazole-(CH_2)_8-nitroarginine]^+, or [ReC_8argNO_2]^+, owing to partial displacement of the water ligand in the active site. From analysis of competitive binding experiments with imidazole, the dissociation constant (K_d) for [ReC_8argNO_2]^+−iNOS_(oxy) was determined to be 3.0 ± 0.1 μM, confirming that the sensitizer-wire binds with higher affinity than both L-arginine (K_d = 22 ± 5 μM) and imidazole (K_d = 14 ± 3 μM). Laser excitation (355 nm) of [ReC_8argNO_2]^+−iNOS_(oxy) triggers electron transfer to the active site of the enzyme, producing a ferroheme in less than ∼1 μs.
Additional Information
© 2007 American Chemical Society. Received: February 19, 2007; In Final Form: April 4, 2007. Publication Date (Web): May 31, 2007. We thank Professor Michael Marletta for materials and assistance in connection with the iNOSoxy preparation. Our work was supported by NIH and the Ellison Medical Foundation (Senior Scholar in Aging to H.B.G.).Attached Files
Accepted Version - nihms62407.pdf
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Additional details
- PMCID
- PMC2596599
- Eprint ID
- 77859
- DOI
- 10.1021/jp071405+
- Resolver ID
- CaltechAUTHORS:20170531-130123854
- NIH
- Ellison Medical Foundation
- Created
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2017-05-31Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field