Structure and Properties of a Bis-Histidyl Ligated Globin from Caenorhabditis elegans,

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• 作者：Jungjoo Yoon ; Mark A. Herzik ; Jr. ; Michael B. Winter ; Rosalie Tran ; Charles Olea ; Jr. ; Michael A. Marletta
• 刊名：Biochemistry
• 出版年：2010
• 出版时间：July 13, 2010
• 年：2010
• 卷：49
• 期：27
• 页码：5662-5670
• 全文大小：925K
• 年卷期：v.49,no.27(July 13, 2010)
• ISSN：1520-4995

文摘

Globins are heme-containing proteins that are best known for their roles in oxygen (O₂) transport and storage. However, more diverse roles of globins in biology are being revealed, including gas and redox sensing. In the nematode Caenorhabditis elegans, 33 globin or globin-like genes were recently identified, some of which are known to be expressed in the sensory neurons of the worm and linked to O₂ sensing behavior. Here, we describe GLB-6, a novel globin-like protein expressed in the neurons of C. elegans. Recombinantly expressed full-length GLB-6 contains a heme site with spectral features that are similar to those of other bis-histidyl ligated globins, such as neuroglobin and cytoglobin. In contrast to these globins, however, ligands such as CO, NO, and CN⁻ do not bind to the heme in GLB-6, demonstrating that the endogenous histidine ligands are likely very tightly coordinated. Additionally, GLB-6 exhibits rapid two-state autoxidation kinetics in the presence of physiological O₂ levels as well as a low redox potential (−193 ± 2 mV). A high-resolution (1.40 Å) crystal structure of the ferric form of the heme domain of GLB-6 confirms both the putative globin fold and bis-histidyl ligation and also demonstrates key structural features that can be correlated with the unusual ligand binding and redox properties exhibited by the full-length protein. Taken together, the biochemical properties of GLB-6 suggest that this neural protein would most likely serve as a physiological sensor for O₂ in C. elegans via redox signaling and/or electron transfer.