Cold Body Temperature as an Evolutionary Shaping force in the Physiology of Antarctic Fishes

0125890 SidellNotothenioid鱼类在南极洲周围的鱼类区系中占主导地位，在其整个生命史中，在体温几乎恒定的情况下进化了1000 - 1400万年。因此，这组动物特别适合于旨在理解和识别低温下进化过程中产生的生理学和生物化学特征的研究。该项目有三个主要目标，旨在研究在寒冷环境中生活的适应性：1。确定脂肪酰辅酶A合成酶（FACS）的脂肪酸结合口袋中的氨基酸取代，解释其底物特异性。脂肪酸是南极鱼类能量代谢的主要燃料。FACS催化CoASH和脂肪酸缩合为脂肪酰基CoA酯，这是这些重要化合物随后代谢所需的步骤。这项研究可能使我们能够解决特定的氨基酸取代，解释底物特异性和在寒冷的生理温度下保持Notothenioid FACS的催化速率。从南极鱼类的白色中轴肌肉组织中产生细胞内钙结合蛋白，小白蛋白的严格的生物化学和生物物理特性。小清蛋白在促进快速收缩肌肉的松弛阶段中起着关键作用，并且是强选择性压力的可能部位。初步数据有力地表明，南极鱼类的蛋白质已被修改，以确保在寒冷的温度下的功能。一套物理技术将被用来确定南极鱼parvalbumins的钙和镁的解离常数和离子从蛋白质解离的单向速率常数。南极鱼小清蛋白全长cDNA克隆将允许推导一级氨基酸序列这些数据将产生洞察的结构元件，允许蛋白质从南极鱼类在非常冷的体温下发挥作用。对南极亚目中心肌肌红蛋白的表达模式进行广泛的调查。以前的工作表明，一个家庭的南极notothenioid鱼（鱼科，冰鱼）的心脏中的细胞内氧结合蛋白，肌红蛋白（Mb）的存在或不存在的变量模式。由于Mb在表达蛋白质的物种中具有生理价值，因此观察到的种间表达模式归因于南大洋中异常低的生态位竞争。这导致预测，类似的损失心脏Mb应观察到其他notothenioid类群。该项目的这一部分将调查尽可能多的脊索动物中是否存在心脏Mb，如果检测到Mb缺乏的物种，将扩展分析，以确定使用分子生物学技术导致其表达丧失的机制。

0125890SidellNotothenioid fishes that dominate the fish fauna surrounding Antarctica have been evolving for 10-14 million years at a nearly constant body temperature of ~0C throughout their life histories. As a result, this group of animals is uniquely suited to studies aimed at understanding and identifying features of physiology and biochemistry that result from the process of evolution at cold body temperature. This project has three major objectives aimed at examining adaptations for life in cold environments: 1. Identify the amino acid substitutions in the fatty acid-binding pocket of fatty acyl CoA synthetase (FACS) that explain its substrate specificity. Fatty acids are a major fuel of energy metabolism in Antarctic fishes. FACS catalyzes the condensation of CoASH and fatty acids to fatty acyl CoA esters, a step required for subsequent metabolism of these important compounds. This research may permit us to resolve the specific amino acid substitutions that explain both substrate specificity and preservation of catalytic rate of notothenioid FACS at cold physiological temperatures.2. Produce a rigorous biochemical and biophysical characterization of the intracellular calcium-binding protein, parvalbumin, from white axial musculature of Antarctic fishes. Parvalbumin plays a pivotal role in facilitating the relaxation phase of fast-contracting muscles and is a likely site of strong selective pressure. Preliminary data strongly indicate that the protein from Antarctic fishes has been modified to ensure function at cold temperature. A suite of physical techniques will be used to determine dissociation constants of Antarctic fish parvalbumins for calcium and magnesium and unidirectional rate constants of ion-dissociation from the protein. Full-length cDNA clones for Antarctic fish parvalbumin(s) will permit deduction of primary amino acid sequence These data will yield insight into structural elements that permit the protein from notothenioid fishes to function at very cold body temperature.3. Conduct a broad survey of the pattern of cardiac myoglobin expression in the Suborder Notothenoidei. Previous work has indicated a variable pattern of presence or absence of the intracellular oxygen-binding protein, myoglobin (Mb), in hearts of one family of Antarctic notothenioid fishes (Channichthyidae; icefishes). Because Mb is of physiological value in species that express the protein, the observed pattern of interspecific expression has been attributed to unusually low niche competition in the Southern Ocean. This leads to the prediction that similar loss of cardiac Mb should be observed in other notothenioid taxa. This part of the project will survey for the presence and absence of cardiac Mb in as many notothenioid species as possible and, if Mb-lacking species are detected, will extend analyses to determine the mechanism(s) responsible for loss of its expression using molecular biological techniques.