Max Planck Institute for Molecular Genetics, Ihnestresse 63-73, 14195, Berlin, Germany.
BMC Evol Biol. 2012 May 11;12:62. doi: 10.1186/1471-2148-12-62.
Uncoupling proteins (UCP) are evolutionary conserved mitochondrial carriers that control energy metabolism and therefore play important roles in several physiological processes such as thermogenesis, regulation of reactive oxygen species (ROS), growth control, lipid metabolism and regulation of insulin secretion. Despite their importance in various physiological processes, their molecular function remains controversial. The evolution and phylogenetic distribution may assist to identify their general biological function and structure-function relationships. The exact number of uncoupling protein genes in the fish genome and their evolution is unresolved.
Here we report the first characterisation of UCP gene family members in sea bass, Dicentrarchus labrax, and then retrace the evolution of the protein family in vertebrates. Four UCP genes that are shared by five other fish species were identified in sea bass genome. Phylogenetic reconstitution among vertebrate species and synteny analysis revealed that UCP1, UCP2 and UCP3 evolved from duplication events that occurred in the common ancestor of vertebrates, whereas the novel fourth UCP originated specifically in the teleost lineage. Functional divergence analysis among teleost species revealed specific amino acid positions that have been subjected to altered functional constraints after duplications.
This work provides the first unambiguous evidence for the presence of a fourth UCP gene in teleost fish genome and brings new insights into the evolutionary history of the gene family. Our results suggest functional divergence among paralogues which might result from long-term and differential selective pressures, and therefore, provide the indication that UCP genes may have diverse physiological functions in teleost fishes. Further experimental analysis of the critical amino acids identified here may provide valuable information on the physiological functions of UCP genes.
解偶联蛋白（UCP）是进化上保守的线粒体载体，控制着能量代谢，因此在许多生理过程中发挥着重要作用，如产热、活性氧（ROS）的调节、生长控制、脂质代谢和胰岛素分泌的调节。尽管它们在各种生理过程中很重要，但它们的分子功能仍然存在争议。进化和系统发生分布可能有助于确定其一般生物学功能和结构-功能关系。鱼类基因组中解偶联蛋白基因的确切数量及其进化尚未解决。
本文首次对鲈鱼（Dicentrarchus labrax）的 UCP 基因家族成员进行了特征描述，然后追溯了该蛋白家族在脊椎动物中的进化历程。在鲈鱼基因组中鉴定出了 4 种与其他 5 种鱼类共享的 UCP 基因。在脊椎动物物种中的系统发育重建和基因排列分析表明，UCP1、UCP2 和 UCP3 是由脊椎动物共同祖先发生的复制事件进化而来的，而新型的第四个 UCP 则专门起源于硬骨鱼谱系。对硬骨鱼物种的功能分化分析揭示了特定的氨基酸位置，这些位置在复制后经历了功能约束的改变。
这项工作首次明确证明了第四个 UCP 基因存在于硬骨鱼的基因组中，并为该基因家族的进化历史提供了新的见解。我们的结果表明，旁系同源物之间存在功能分化，这可能是由于长期和不同的选择压力所致，因此表明 UCP 基因在硬骨鱼中可能具有多种生理功能。对这里鉴定的关键氨基酸进行进一步的实验分析可能会提供有关 UCP 基因生理功能的有价值信息。
