Proton NMR investigation of the reconstitution of equine myoglobin with hemin dicyanide Evidence for late formation of the proximal His93F8‐iron bond

FEBS Letters

Peyton, David H.¹  Yee, Sidney¹ 

[1] Chemistry Department, Portland State University, Portland, Oregon, USA 97207-0751

关键词: Heme;    Myoglobin;    NMR;    EqMb;    equine myoglobin;    FePPIX;    iron (III) protoporphyrin IX;    hemin;    FePPIX(CN)2;    hemin dicyanide;    Mb;    myoglobin;    NMR;    nuclear magnetic resonance spectroscopy;    PPIX;    protoporphyrin IX;    SwMb;    sperm whale myoglobin;   

DOI  :  10.1016/0014-5793(91)81240-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Reconstitution of apoequine myoglobin (apoEqMb) with hemin dicyanide (FePPIX(CN)₂) was monitored by ¹H NMR spectroscopy to gain information about the sequence of events leading to metEqMbCN. At least one step in the pathway is slow enough to allow us to follow the time-dependence of formation of the product, a mixture of heme-insertion isomers characterized by others (Jue, T., Krishnamoorthi, R. and La Mar, G.N. (1983) J. Am. Chem. Soc. 105, 5701–5703; Lecomte, J.T.J., Johnson, R.D. and La Mar, G.N. (1985) Biochim. Biophys. Acta 829, 268–274). However, in contrast to all previously reported Mb-FePPIX reconstitutions, we find that the initial ratio of heme-insertion isomers is not 1:1. This mixture is, instead, found to be enhanced in the isomer which dominates at equilibrium. This is taken as evidence for a ‘[FePPIX(CN)₂·EqMb]’ intermediate which lacks the proximal His⁹³F8-Fe bond and which proceeds quickly toward an equilibrium ratio of heme-insertion isomers. Therefore the heme-insertion isomer ratio is frozen only when the proximal His⁹³F8-Fe bond is formed. The difference in this ratio of heme-insertion isomers between EqMb(4,5:1) and SwMb(2.5:1) likely reflects the amino acid substitution: Lys→Arg⁴⁵CD3(EqMb→SwMb).

【 授权许可】

Unknown