Uchida Takeshi, Stevens Julie M, Daltrop Oliver, Harvat Edgar M, Hong Lin, Ferguson Stuart J, Kitagawa Teizo
Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Myodaiji, Okazaki, Aichi 444-8787, Japan.
J Biol Chem. 2004 Dec 10;279(50):51981-8. doi: 10.1074/jbc.M408963200. Epub 2004 Oct 1.
The heme chaperone CcmE is a novel protein that binds heme covalently via a histidine residue as part of its essential function in the process of cytochrome c biogenesis in many bacteria as well as plant mitochondria. In the continued absence of a structure of the holoform of CcmE, identification of the heme ligands is an important step in understanding the molecular function of this protein and the role of covalent heme binding to CcmE during the maturation of c-type cytochromes. In this work, we present spectroscopic data that provide insight into the ligation of the heme iron in the soluble domain of CcmE from Escherichia coli. Resonance Raman spectra demonstrated that one of the heme axial ligands is a histidine residue and that the other is likely to be Tyr134. In addition, the properties of the heme resonances of the holo-protein as compared with those of a form of CcmE with non-covalently bound heme provide evidence for the modification of one of the heme vinyl side chains by the protein, most likely the 2-vinyl group.
血红素伴侣蛋白CcmE是一种新型蛋白质，它通过组氨酸残基与血红素共价结合，这是其在许多细菌以及植物线粒体中细胞色素c生物合成过程中的基本功能的一部分。在CcmE全酶形式的结构仍然缺失的情况下，确定血红素配体是理解该蛋白质分子功能以及在c型细胞色素成熟过程中血红素与CcmE共价结合作用的重要一步。在这项工作中，我们提供了光谱数据，这些数据有助于深入了解来自大肠杆菌的CcmE可溶性结构域中血红素铁的配位情况。共振拉曼光谱表明，血红素的一个轴向配体是组氨酸残基，另一个可能是Tyr134。此外，与具有非共价结合血红素的CcmE形式相比，全蛋白血红素共振的特性为蛋白质对血红素乙烯基侧链之一（很可能是2-乙烯基）的修饰提供了证据。
