Structural analysis of monomeric hemichrome and dimeric cyanomet hemoglobins from Caudina arenicola.
Structural analysis of monomeric hemichrome and dimeric cyanomet hemoglobins from Caudina arenicola.
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来自 Caudina arenicola 的单体半色素和二聚氰基血红蛋白的结构分析。
DOI：
10.1006/jmbi.1995.0445
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发表时间：
1995
影响因子：
5.6
通讯作者：
Hackert,ML
中科院分区：
文献类型：
--
作者：
Mitchell,DT;Kitto,GB;Hackert,ML
从海参caudina arenicola（一种棘皮动物）中测定了两种血红蛋白（Hb）的x射线结构：低自旋、半色单体Hb- c链和氰氨基配体二聚体Hb- d链。试图从同一链型中获得脱氧配体和半色原形式的晶体结构尚未成功。在这项工作中，我们比较了Hb-C链和Hb-D链的结构，并观察到与该生物血红蛋白链的不同配体状态相关的三级结构的差异。除了远端组氨酸和E螺旋的移位外，血红素基团在血红素口袋中的位置、血红素基团与蛋白质的氢键以及D螺旋的状态也存在差异。这些差异对于理解这些血红蛋白的配体结合状态很重要。Hb-D同型二聚体的四元结构与来自scapharca inaequivalvisandUrechis caupo的另外两种无脊椎血红蛋白的四元结构进行了比较，这两种蛋白也具有亚基-亚基相互作用，涉及E和E '螺旋。二聚体之间的相互作用是非常不同的。然而，在cyanomet Hb-D中观察到的二聚体界面与从蛤（Scapharca）中观察到的一氧化碳血红蛋白二聚体惊人地相似，然而，许多与Scapharca血红蛋白合作机制相关的关键氨基酸残基在caapharca血红蛋白中并不保守。
The X-ray structures of two hemoglobins (Hb) from the sea cucumberCaudina arenicola(an echinoderm) have been determined: a low spin, hemichrome, monomeric Hb-C chain, and a cyanomet-liganded dimeric Hb-D chain. Attempts to obtain crystal structures of the deoxy-liganded and hemichrome forms from the same chain type have not been successful. In this work, the Hb-C chain and Hb-D chain structures are compared, and differences observed in tertiary structure related to the different ligand states for hemoglobin chains from this organism. In addition to shifts of the distal histidine and E helix, differences are noted in the position of the heme group within the heme pocket, the hydrogen bonding of the heme group to the protein, and the status of the D helix. These differences are important in understanding the ligand-linked association states of these hemoglobins. The quaternary structure of the Hb-D homodimer is compared with those from two other invertebrate hemoglobins fromScapharca inaequivalvisandUrechis caupo, which also have subunit–subunit interactions that involve the E and E′ helices. The dimer interactions of theCaudinaandUrechishemoglobins are quite dissimilar. However, the dimer interface observed in cyanomet Hb-D is strikingly similar to that observed for the carbonmonoxy hemoglobin dimer from the clam,Scapharca, yet many of the key amino acid residues implicated in the cooperative mechanism of theScapharcahaemoglobin are not conserved in theCaudinahemoglobins.