Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence.

Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence. Research Abstract Details 

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Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence. Abstract Text:

Mohammed Ibrahim,Robert L Kerby,Mrinalini Puranik,Ingar H Wasbotten,Hwan Youn,Gary P Roberts,Thomas G Spiro,

The heme-containing protein CooA of Rhodospirillum rubrum regulates the expression of genes involved in CO oxidation. CooA binds its target DNA sequence in response to CO binding to its heme. Activity measurements and resonance Raman (RR) spectra are reported for CooA variants that bind DNA even in the absence of CO, those in which the wild-type residues at the 121-126 positions, TSCMRT, are replaced by the residues AYLLRL or RYLLRL, and also for variants that bind DNA poorly in the presence of CO, such as L120S and L120F. The Fe-C and C-O stretching resonance Raman (RR) frequencies of all CooAs examined deviate from the expected back-bonding correlation in a manner indicating weakening of the Fe-His-77 proximal ligand bond, and the extent of weakening correlates positively with DNA binding activity. The (A/R) YLLRL variants have detectable populations of a 5-coordinate heme resulting from partial dissociation of the endogenous distal ligand, Pro-2. Selective excitation of this population reveals downshifted Fe-His-77-stretching RR bands, confirming the proximal bond weakening. These results support our previous hypothesis that the conformational change required for DNA binding is initiated by displacement of the heme into an adjacent hydrophobic cavity once CO displaces the Pro-2 ligand. Examination of the crystal structure reveals a physical basis for these results, and a mechanism is proposed to link heme displacement to conformational change.

Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence. Publishing Authors By Initials

M Ibrahim,RL Kerby,M Puranik,IH Wasbotten,H Youn,GP Roberts,TG Spiro,

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Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence. Journal Published:

PUBLICATION TYPE: Research Support, N.I.H., Extr

Journal: The Journal of biological chemistry

VOLUME: 281

Page Numbers: 29165-73

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ISSN: 0021-9258

DAY: 26

MONTH: 07

YEAR: 2006

Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence. Information

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LANGUAGE: eng

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Grant and Affiliation Information for Heme displacement mechanism of CooA activation: mutational and Raman spectroscopic evidence.

AFFILIATION: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.

Country: United States

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MEDLINETA: J Biol Chem

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