滨螺卓越的耐高温能力，温度耐受上限竟高达55℃——潮间带 Echinolittorina 属滨螺细胞质苹果酸脱氢酶高温耐受机制的研究

研究团队以分布于高潮间带，具有高耐热性的两种滨螺为研究对象，通过生理生化学实验及计算机模拟手段，发现耐热的软体动物通过增强代谢关键酶的作用，避免了在高温条件下的解链；研究团队还提出，局部柔性的增长使得酶在低温条件下能够发挥其催化功能，同时能在极端高温条件下，起到稳定蛋白质的作用，确保了蛋白质功能的维持。这些发现对于查明环境温度对生物分布的影响及其机制，预测气候变暖的生态学效应将具有重要意义。 滨螺广泛分布于潮间带高潮区，是潮间带垂直分布区划分的标志性物种。塔结节滨螺（Echinolittorina malaccana）和粒结节滨螺（E. radiata）是我国岩相潮间带高潮区常见物种，其温度耐受上限高达 55-60°C。董云伟教授团队与美国斯坦福大学 George Somero 教授，以及华侨大学张光亚教授团队合作，进行了一系列研究，探索了高热耐受性滨螺在极端高温条件下，仍旧保持体内蛋白质微结构的完整、功能的维持的奥妙所在。【Abstract】Snails of the genus Echinolittorina are among the most heat-tolerant animals; they experience average body temperatures near 41–44℃ in summer and withstand temperatures up to at least 55℃. Here, we demonstrate that heat stability of function (indexed by the Michaelis–Menten constant of the cofactor NADH, KMNADH) and structure (indexed by rate of denaturation) of cytosolic malate dehydrogenases (cMDHs) of two congeners (E. malaccana and E. radiata) exceeds values previously found for orthologs of this protein from less thermophilic species. The ortholog of E. malaccana is more heat stable than that of E. radiata, in keeping with the congeners' thermal environments. Only two inter-congener differences in amino acid sequence in these 332 residue proteins were identified. In both cases (positions 48 and 114), a glycine in the E. malaccana ortholog is replaced by a serine in the E. radiata protein. To explore the relationship between structure and function and to characterize how amino acid substitutions alter stability of different regions of the enzyme, we used molecular dynamics simulation methods. These computational methods allow determination of thermal effects on fine-scale movements of protein components, for example, by estimating the root mean square deviation in atom position over time and the root mean square fluctuation for individual residues. The minor changes in amino acid sequence favor temperature-adaptive change in flexibility of regions in and around the active sites. Interspecific differences in effects of temperature on fine-scale protein movements are consistent with the differences in thermal effects on binding and rates of heat denaturation.This research was substantially supported by grants from National Natural Science Foundation of China (41476115), Program for New Century Excellent Talents of Ministry of Education, China, Nature Science Foundation for Distinguished Young Scholars of Fujian Province (2017J07003), China and the State Key Laboratory of Marine Environmental Science Internal Program, Xiamen University (MELRI1501)