Blood flow regulation by S-nitrosohemoglobin in the physiological oxygen gradient.
The binding of oxygen to heme irons in hemoglobin promotes the binding of nitric oxide (NO) to cysteinebeta93, forming S-nitrosohemoglobin. Deoxygenation is accompanied by an allosteric transition in S-nitrosohemoglobin [from the R (oxygenated) to the T (deoxygenated) structure] that releases the NO group. S-nitrosohemoglobin contracts blood vessels and decreases cerebral perfusion in the R structure and relaxes vessels to improve blood flow in the T structure. By thus sensing the physiological oxygen gradient in tissues, hemoglobin exploits conformation-associated changes in the position of cysteinebeta93 SNO to bring local blood flow into line with oxygen requirements.
Stamler, JS; Jia, L; Eu, JP; McMahon, TJ; Demchenko, IT; Bonaventura, J; Gernert, K; Piantadosi, CA
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