Ferreras José M, Ragucci Sara, Citores Lucía, Iglesias Rosario, Pedone Paolo V, Di Maro Antimo
Department of Biochemistry and Molecular Biology and Physiology, Faculty of Sciences, University of Valladolid, E-47011 Valladolid, Spain.
Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, I-81100 Caserta, Italy.
Int J Biol Macromol. 2016 Dec;93(Pt A):1041-1050. doi: 10.1016/j.ijbiomac.2016.09.065. Epub 2016 Sep 19.
Myoglobin (Mb) is studied to clarify the structure-function relationships in protein science. In this work, we report the results of a comparative analysis of amino acid sequences from 298 vertebrate Mbs. Forty-one high conserved residues were identified and seven of them were invariants [E18, G25, F43, V68, L72, H93 (proximal histidine) and H97]. E18 is the only invariant amino acid residue located out of the heme-pocket and Xe-cavities playing a role in interaction between the A and E-helices. A comparative analysis of several parameters related to amino acid composition shows an increase of average mass, accessible surface area and volume per residue from Actinopterygii to Mammalia and Aves. This may be due to an increased number of bulky residues reducing the non-specific cavities volume and thus improving the oxygen flow between the heme site and the outside of the protein. Finally, the phylogenetic analyses of Mb in vertebrates are consistent with an evolution that runs with the diversification of the species, but in which several episodes of gene duplication and lost have occurred, less frequently in the ancestors of great taxons, cartilaginous fishes and non-avian reptiles, most frequently in ray-finned fishes and mammals, and very frequently in birds.
为阐明蛋白质科学中的结构-功能关系，对肌红蛋白（Mb）展开了研究。在这项工作中，我们报告了对298种脊椎动物肌红蛋白氨基酸序列的比较分析结果。鉴定出41个高度保守的残基，其中7个是不变残基[E18、G25、F43、V68、L72、H93（近端组氨酸）和H97]。E18是唯一位于血红素口袋和Xe腔之外的不变氨基酸残基，在A螺旋和E螺旋之间的相互作用中发挥作用。对与氨基酸组成相关的几个参数进行比较分析表明，从辐鳍鱼纲到哺乳纲和鸟纲，平均质量、可及表面积和每个残基的体积均有所增加。这可能是由于大量残基数量增加，减少了非特异性腔的体积，从而改善了血红素位点与蛋白质外部之间的氧气流动。最后，脊椎动物肌红蛋白的系统发育分析与物种多样化的进化过程一致，但其中发生了几次基因复制和丢失事件，在大型分类群的祖先、软骨鱼和非鸟类爬行动物中发生频率较低，在硬骨鱼和哺乳动物中最频繁，在鸟类中非常频繁。
