Truncated Hemoglobins: A New Family of Hemoglobins Widely Distributed in Bacteria, Unicellular Eukaryotes, and Plants* 210
Truncated Hemoglobins: A New Family of Hemoglobins Widely Distributed in Bacteria, Unicellular Eukaryotes, and Plants* 210
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DOI：
10.1074/jbc.r100058200
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发表时间：
2002-01
期刊：
影响因子：
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通讯作者：
J. Wittenberg;M. Bolognesi;B. Wittenberg;M. Guertin
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文献类型：
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作者：
J. Wittenberg;M. Bolognesi;B. Wittenberg;M. Guertin
(1) 构成分布于真细菌、蓝细菌、原生动物和植物中的小氧结合血红素蛋白家族（表 I，补充材料），在血红蛋白 (Hb) 超家族中形成一个独特的群体 (2)。它们在植物界几乎无处不在，存在于许多侵袭性致病细菌中，并且被认为具有非常古老的起源。在古细菌或后生动物的基因组中尚未检测到任何物质。从特征上看，trHb 在细胞内浓度为纳摩尔至微摩尔，暗示其可能发挥催化蛋白的作用。许多 trHb 显示的氨基酸序列比非脊椎动物血红蛋白短 20-40 个残基，而它们与非脊椎动物血红蛋白之间的序列相似性几乎不相关。晶体结构 (1,3) 显示 trHb 三级结构基于 2-on-2-hel-ical 三明治，这代表了对高度保守的珠蛋白折叠的前所未有的编辑。此外，几乎连续的疏水隧道，从分子表面穿过蛋白质基质到血红素远端位点，可以提供配体扩散到血红素的路径。
(1) constitute a family ofsmall oxygen-binding heme proteins distributed in eubacteria,cyanobacteria, protozoa, and plants (Table I, SupplementalMaterial) forming a distinct group within the hemoglobin (Hb)superfamily (2). They are nearly ubiquitous in the plant king-dom, occur in many aggressively pathogenic bacteria, and areheld to be of very ancient origin. None have been detected inthe genomes of archaea or metazoa. Characteristically, trHbsoccur at nano- to micromolar intracellular concentration, hint-ing at a possible role as catalytic proteins.Many trHbs display amino acid sequences 20–40 residuesshorter than non-vertebrate hemoglobins to which they arescarcely related by sequence similarity. Crystal structures (1,3) show that trHb tertiary structure is based on a 2-on-2 -hel-ical sandwich, which represents an unprecedented editing ofthe highly conserved globin fold. Moreover, an almost continu-ous hydrophobic tunnel, traversing the protein matrix from themolecular surface to the heme distal site, may provide a pathfor ligand diffusion to the heme.