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首页> 外文期刊>Biochemistry >Asymmetric cyanomet valency hybrid hemoglobin, (alpha(+CN-)beta(+CN-))(alpha beta): The issue of valency exchange
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Asymmetric cyanomet valency hybrid hemoglobin, (alpha(+CN-)beta(+CN-))(alpha beta): The issue of valency exchange

机译：不对称的氰基化合价混合血红蛋白，（alpha（+ CN-）beta（+ CN-））（alpha beta）：化合价交换的问题

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A new framework for hemoglobin cooperativity was proposed by Ackers and colleagues on the basis of the hyper thermodynamic stability and deoxy (T) quaternary structure of one of diliganded deoxy-cyanomet hybrid hemoglobins, (alpha(+CN-)beta(+CN-))(alpha beta), studied by hybridization of the equimolar mixture of deoxyhemoglobin and cyanomethemoglobin through a long (70-100 h) dimer exchange reaction [Daugherty et al. (1991) Proc. Natl. Acad, Sci. U.S.A. 88, 1110-1114]. Recently, we reported that the published hyperstability of (alpha(+CN-)beta(+CN-))(alpha beta) is incorrect due to the occurrence of valency exchange between the heme sites of both parental hemoglobins during the long deoxy incubation [Shibayama et al. (1997) Biochemistry 36, 4375-4381]. We also noted a difficulty in maintaining both anaerobicity and excess free cyanide of the sample during the long incubation, which led to formation of cyanide-unbound aqometheme in the original deoxyhemoglobin resulting from the electron transfer to cyanometheme. This paper is a response to a recent argument against our work [Ackers et al. (1997) Biochemistry 36 10822-10829]. Ackers et al. have claimed that no appreciable formation of aqomethemoglobin with their methods ensures their sample integrity, based on a supposition that our observed valency exchange may have occurred via aqometheme. In this paper, however, we demonstrate that appreciable (>27%) valency exchange really occurs between deoxy and cyanometheme sites during 72 h incubation under conditions where both anaerobicity and excess free cyanide of the sample solution are maintained by a continuous flow of humidified N-2 With HCN. This confirms our view that previous experimental data on (alpha(+CN-)beta(+CN-))(alpha beta) Obtained by the long incubations should be subject to reexamination while our earlier estimation of a lower limit of free energy of (alpha(+CN-)beta(+CN-))(alpha beta) (i.e., greater than or equal to -10.1 kcal/mol) by a rapid method (35 min) is still valid. We also suggest a possibility that the T quaternary structure of (alpha(+CN-)beta(+CN-))(alpha beta) assigned by Ackers and colleagues using the long incubations is an artifact arising from the valency exchange, These results suggest that the putative mechanistic picture for hemoglobin cooperativity inferred from studies on deoxy-cyanomet hybrids is without foundation. [References: 34]
机译：Ackers及其同事基于双配体脱氧-氰基杂交血红蛋白（α（+ CN-）beta（+ CN-）的超热力学稳定性和脱氧（T）季结构，提出了一种新的血红蛋白协同性框架。 ）（αbeta），通过长时间（70-100 h）二聚体交换反应，使脱氧血红蛋白和氰化血红蛋白的等摩尔混合物杂交而研究[Daugherty等。 （1991）美国国家科学院院刊。 Natl。 Acad，科学。 U.S.A. 88，1110-1114]。最近，我们报道，由于长时间脱氧孵育过程中，两个亲本血红蛋白的血红素位点之间发生了价态交换，因此已发布的（alpha（+ CN-）beta（+ CN-））（alpha beta）超稳定性不正确[芝山等。 （1997）Biochemistry 36，4375-4381]。我们还注意到，在长时间孵育过程中难以同时保持厌氧性和过量的游离氰化物，这导致了原始脱氧血红蛋白中的氰化物未结合的质子素的形成，这是由于电子转移至质子素而引起的。本文是对最近反对我们工作的争论的回应[Ackers等。 （1997）Biochemistry 36 10822-10829]。 Ackers等。根据我们的观察到的化合价交换可能已经通过水质发生的假设，他们声称用它们的方法没有形成明显的水溶质血红蛋白来确保其样品完整性。但是，在本文中，我们证明了在连续不断的加湿N维持厌氧性和过量游离氰化物的条件下，在72 h孵育过程中，脱氧和蓝素位置之间确实发生了相当大的（> 27％）化合价交换。 -2使用HCN。这证实了我们的观点，即通过长时间孵育获得的有关（alpha（+ CN-）beta（+ CN-））（alpha beta）的先前实验数据应进行重新检验，而我们先前对（通过快速方法（35分钟）获得的alpha（+ CN-）beta（+ CN-））αalpha（即大于或等于-10.1 kcal / mol）仍然有效。我们还提出了这样的可能性，即Ackers和同事使用长时间孵育分配的（alpha（+ CN-）beta（+ CN-））（alpha beta）的T四元结构是化合价交换引起的假象，这些结果表明从脱氧-氰基杂种的研究中推断出的血红蛋白协同性的机制机理是没有根据的。 [参考：34]

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