Trittelvitz E, Gersonde K, Winterhalter K H
Eur J Biochem. 1975 Feb 3;51(1):33-42. doi: 10.1111/j.1432-1033.1975.tb03903.x.
At 77 K the electron spin resonance (ESR) spectra of the NO derivatives of the mutant haemoglobins Hb M Iwate and Hb Zurich as well as of the isolated chains of normal haemoglobin were studied. Two types of ESR spectra differing in the g-value and the hyperfine splitting at gzz were observed. The type II spectrum is characterized by a hyperfine structure at gzz = 2.005 with a splitting constant of deltaH = 23 G (14NO) or 32 G (15NO), respectively. In the type I spectrum the splitting constant of the hyperfine structure at gzz = 2.009 amounts to deltaH = 18 G (14NO) or 23 G (15NO), respectively. In some cases this hyperfine structure is coincident with another one at gxx = 2.064 with nearly identical splitting constant. In addition, the type I spectrum is characterized by an increased ESR absorption at gxx = 2.064. At neutral pH the NO derivatives of the isolated chains as well as of the mutant haemoglobins give rise to a type II spectrum. In correspondence with previous results gained with normal NO haemoglobin, the ESR spectra of the NO-alpha chains and NO-Hb Zurich show a transition to type I in the acid region. This transition is favoured by binding of 2,3-bisphosphoglycerate. On the other hand, the ESR spectra of the NO-beta chains and NO-Hb M Iwate are of the type II also at acid pH. The NO-beta chains show a transition of the ESR spectrum from type II to type I only at alkaline pH. These results indicate that in the tetrameric NO haemoglobin only the alpha chains are responsible for the transition of the ESR spectrum from type II to type I in the acid region. The two types of ESR spectra are interpreted in terms of two kinds of haem-NO complexes differing in the iron-NO and iron-imidazole distances. The type II spectrum is attributed to a complex with a relatively short iron-imidazole distance which is responsible for a weakened sigma-bond in trans position. The type I spectrum arises then from a complex with a larger iron-imidazole bond leading to an approach of the NO molecule to the iron. The influence of the protein conformation upon the iron-imidazole bond length is discussed with regard to the ESR spectra of the mutant NO haemoglobins and considering the influence of agents modifying the protein structure.
在77K温度下，研究了突变血红蛋白Hb M岩手和Hb苏黎世的NO衍生物以及正常血红蛋白分离链的电子自旋共振（ESR）光谱。观察到两种ESR光谱，它们在g值和gzz处的超精细分裂有所不同。II型光谱的特征是在gzz = 2.005处有超精细结构，分裂常数分别为δH = 23G（14NO）或32G（15NO）。在I型光谱中，gzz = 2.009处超精细结构的分裂常数分别为δH = 18G（14NO）或23G（15NO）。在某些情况下，这种超精细结构与gxx = 2.064处的另一种超精细结构重合，分裂常数几乎相同。此外，I型光谱的特征是在gxx = 2.064处ESR吸收增加。在中性pH条件下，分离链以及突变血红蛋白的NO衍生物产生II型光谱。与之前用正常NO血红蛋白获得的结果一致，NO-α链和NO-Hb苏黎世的ESR光谱在酸性区域显示向I型转变。这种转变受到2,3-二磷酸甘油酸结合的促进。另一方面，NO-β链和NO-Hb M岩手的ESR光谱在酸性pH下也是II型。NO-β链仅在碱性pH下显示ESR光谱从II型向I型的转变。这些结果表明，在四聚体NO血红蛋白中，只有α链负责酸性区域ESR光谱从II型向I型的转变。两种类型的ESR光谱是根据铁-NO和铁-咪唑距离不同的两种血红素-NO复合物来解释的。II型光谱归因于一种铁-咪唑距离相对较短的复合物，它导致反式位置的σ键减弱。I型光谱则源于一种铁-咪唑键较大的复合物，导致NO分子靠近铁。关于突变NO血红蛋白的ESR光谱，并考虑到修饰蛋白质结构的试剂的影响，讨论了蛋白质构象对铁-咪唑键长度 的影响。
