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Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase.


ABSTRACT: We investigated the changes of heme coordination in purified soluble guanylate cyclase (sGC) by time-resolved spectroscopy in a time range encompassing 11 orders of magnitude (from 1 ps to 0.2 s). After dissociation, NO either recombines geminately to the 4-coordinate (4c) heme (?G1 = 7.5 ps; 97 ± 1% of the population) or exits the heme pocket (3 ± 1%). The proximal His rebinds to the 4c heme with a 70-ps time constant. Then, NO is distributed in two approximately equal populations (1.5%). One geminately rebinds to the 5c heme (?G2 = 6.5 ns), whereas the other diffuses out to the solution, from where it rebinds bimolecularly (? = 50 ?s with [NO] = 200 ?M) forming a 6c heme with a diffusion-limited rate constant of 2 × 10(8) M(-1)?s(-1). In both cases, the rebinding of NO induces the cleavage of the Fe-His bond that can be observed as an individual reaction step. Saliently, the time constant of bond cleavage differs depending on whether NO binds geminately or from solution (?5C1 = 0.66 ?s and ?5C2 = 10 ms, respectively). Because the same event occurs with rates separated by four orders of magnitude, this measurement implies that sGC is in different structural states in both cases, having different strain exerted on the Fe-His bond. We show here that this structural allosteric transition takes place in the range 1-50 ?s. In this context, the detection of NO binding to the proximal side of sGC heme is discussed.

SUBMITTER: Yoo BK 

PROVIDER: S-EPMC4394285 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase.

Yoo Byung-Kuk BK   Lamarre Isabelle I   Martin Jean-Louis JL   Rappaport Fabrice F   Negrerie Michel M  

Proceedings of the National Academy of Sciences of the United States of America 20150323 14


We investigated the changes of heme coordination in purified soluble guanylate cyclase (sGC) by time-resolved spectroscopy in a time range encompassing 11 orders of magnitude (from 1 ps to 0.2 s). After dissociation, NO either recombines geminately to the 4-coordinate (4c) heme (τG1 = 7.5 ps; 97 ± 1% of the population) or exits the heme pocket (3 ± 1%). The proximal His rebinds to the 4c heme with a 70-ps time constant. Then, NO is distributed in two approximately equal populations (1.5%). One g  ...[more]

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