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Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure.

ABSTRACT: Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a "site-specific" homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we show that the site-specific allosteric effect is not necessarily only a unique mechanism of O2 allostery. Our simulation results revealed that the solution environment of high O2 partial pressure enhances the quaternary change from T to R without binding to the heme, suggesting an additional "non-site-specific" allosteric effect of O2. The latter effect should play a complementary role in the quaternary change by affecting the intersubunit contacts. This analysis must become a milestone in comprehensive understanding of the allosteric regulation of HbA from the molecular point of view.

SUBMITTER: Takayanagi M

PROVIDER: S-EPMC3978498 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure.

Takayanagi Masayoshi M Kurisaki Ikuo I Nagaoka Masataka M

Scientific reports 20140408

Protein allostery is essential for vital activities. Allosteric regulation of human hemoglobin (HbA) with two quaternary states T and R has been a paradigm of allosteric structural regulation of proteins. It is widely accepted that oxygen molecules (O2) act as a "site-specific" homotropic effector, or the successive O2 binding to the heme brings about the quaternary regulation. However, here we show that the site-specific allosteric effect is not necessarily only a unique mechanism of O2 alloste ...[more]

PMID: 24710521

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Project description:BackgroundTemporary circulatory support is a bridge between acute circulatory failure and definitive treatment or recovery. Currently, venoarterial extracorporeal membrane oxygenation (VA-ECMO) is considered to be one of the effective circulatory support methods, although cardiac function monitoring during the treatment still needs further investigation. Inflection point of arterial oxygen partial pressure (IPPaO2) may occur at an early stage in part of patients with a good prognosis after VA-ECMO treatment, and the relationship between time of IPPaO2 (tIPPaO2) and recovery of cardiac function or prognosis remains unclear.MethodsTo investigate this relationship, we retrospectively analyzed the clinical data of 71 patients with different conditions after treatment with VA-ECMO in the emergency center of Jiangsu Province Hospital between May 2015 and July 2020. Spearman's correlation analysis was used for the correlation between tIPPaO2 and quantitative data, and ROC curve for the predictive effect of tIPPaO2 on the 28-day mortality.ResultsThirty-five patients were admitted because of refractory cardiogenic shock (26 of 35 survived) and the remaining 36 patients due to cardiac arrest (13 of 36 survived). The overall survival rate was 54.9% (39 of 71 survived). Acute physiology and chronic health evaluation II, ECMO time, tIPPaO2, continuous renal replacement therapy time, mechanical ventilation time, and bleeding complications in the survival group were lower than those in the non-survival group, with length of stay, intensive care unit stay, and platelet levels were being higher. The tIPPaO2 was negatively correlated with ejection fraction, and the shorter tIPPaO2 resulted in a higher 28-day survival probability, higher predictive value for acute myocardial infarction and fulminant myocarditis.ConclusionsTherefore, tIPPaO2 could be a reliable qualitative indicator of cardiac function in patients treated with VA-ECMO, which can reveal appropriate timing for adjusting VA-ECMO flow or weaning.Trial registrationChiCTR1900026105 .

Dataset Information

Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure.

Publications

Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure.

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