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首页> 外文期刊>Journal of Proteins and Proteomics >TRUNCATED OR 2/2 HEMOGLOBINS : A NEW CLASS OF GLOBINS WITH NOVEL STRUCTURE AND FUNCTION
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TRUNCATED OR 2/2 HEMOGLOBINS : A NEW CLASS OF GLOBINS WITH NOVEL STRUCTURE AND FUNCTION

机译：截短的或2/2血红蛋白：具有新型结构和功能的一类新的血红蛋白

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Bright red hemoglobins, the most well-known paradigm in protein science, seem to be ubiquitous innature. With advances in modern tools and techniques, discovery of new globins at a rapid pace has expandedthis family. With every discovery, new insights emerged regarding their novel structure, function and severalother characteristics previously not observed for hemoglobins. Even the classical function unanimously assignedto hemoglobins – oxygen transport and storage – needed re-evaluation. The ability of this class of proteins toshow responses against various gaseous ligands, even the poisonous ones, indicate that it is obviously as ancientas life. As organisms evolved, hemoglobins also evolved, and accumulated a great degree of diversity in allaspects. The classical globin fold is very unique with 3-on-3 alpha helical bundle as observed in the traditionaloxygen-transport hemoglobins like myoglobin, human blood hemoglobin and leghemoglobins in plants. However,a class of the newly discovered hemoglobins, which dominate the superfamily and appears ancient in originmostly have 2-on-2 fold, commonly termed as “truncated” hemoglobins. These hemoglobins are phylogeneticallydistinct from their classical counterparts and are often shorter in their polypeptide length by 20-40 residuesmainly due to a lack of short A helix, D helix and F helix. However, hemoglobins with 2-on-2 fold were also laterfound to have polypeptide chain lengths similar in size to classical globins. Disordered pre-F helix region,conserved glycine motifs and other key residues and apolar tunnels through their protein matrix for migrationof ligands are some unique characteristics features of these truncated hemoglobins. Some of these are alsohexacoordinated at heme iron where an amino acid from within the protein coordinates heme iron in absence ofa ligand. These hemoglobins are well known for their high affinity towards ligand and have a diverse mechanismof ligand binding involving tunnel system and operated by “gate” mechanism of conserved residues. Thesehemoglobins seem to act as good detoxificant or scavenger of poisonous gases to protect the harbouring organismin adverse environmental condition. This mechanism might help pathogens harbouring these globins to evadehost defence mechanism during infection. The current review summarizes these findings with regard to truncatedhemoglobins in a comprehensive manner providing insight into structure and function relationship of this novelhemoglobin family.
机译：鲜红的血红蛋白是蛋白质科学中最著名的范例，似乎无处不在。随着现代工具和技术的进步，快速发现新球蛋白已扩展了这个家族。有了每一项发现，关于血红蛋白的新颖结构，功能和其他一些特征的新见解就出现了。甚至血红蛋白的经典功能（氧气的运输和储存）都需要重新评估。这类蛋白质显示出对各种气态配体（甚至是有毒的配体）的反应的能力，表明它显然具有古老的生命。随着生物的进化，血红蛋白也进化，并在各个方面积累了很大程度的多样性。如在植物中的传统氧转运血红蛋白（如肌红蛋白，人血血红蛋白和豆球蛋白）中观察到的，经典的球蛋白折叠在3对3α螺旋束中非常独特。但是，一类新发现的血红蛋白在超家族中占支配地位，并且起源似乎古老，大多具有2对2倍的折叠，通常称为“截短”血红蛋白。这些血红蛋白在系统发育上与经典血红蛋白不同，并且通常在多肽长度上短20-40个残基，这主要是由于缺少短的A螺旋，D螺旋和F螺旋。然而，后来还发现具有2对2倍的血红蛋白具有与经典球蛋白大小相似的多肽链长度。这些截短的血红蛋白具有一些独特的特征，即无序的前F螺旋区，保守的甘氨酸基序和其他关键残基，以及通过其蛋白质基质的非极性通道，以进行配体迁移。其中一些在血红素铁上也是六配位的，其中蛋白质内的氨基酸在没有配体的情况下与血红素铁配位。这些血红蛋白以其对配体的高亲和力而闻名，并具有涉及隧道系统的多种配体结合机制，并通过保守残基的“门”机制进行操作。这些血球蛋白似乎可以作为有毒气体的良好排毒剂或清除剂，以在不利的环境条件下保护庇护生物。这种机制可能有助于携带这些球蛋白的病原体在感染过程中逃避宿主防御机制。本综述以全面的方式总结了有关截短的血红蛋白的这些发现，从而提供了对该新型血红蛋白家族的结构和功能关系的深入了解。

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