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

[125890]南极鱼类是南极周围鱼类动物群的主要组成部分，它们在一生中几乎保持恒定的~0℃的体温下进化了1000 - 1400万年。因此，这一组动物特别适合于旨在理解和识别在低温下进化过程中产生的生理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。鉴定脂肪酸酰基辅酶a合成酶（FACS）的脂肪酸结合袋中的氨基酸取代，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和脂肪酸缩合成脂肪酸酰基CoA酯，这是这些重要化合物后续代谢所需的一个步骤。这项研究可能允许我们解决特定的氨基酸取代，解释底物特异性和notothenioid FACS在冷生理温度下的催化速率保存。对南极鱼类的白色轴向肌肉组织中的细胞内钙结合蛋白小蛋白进行严格的生化和生物物理表征。小白蛋白在促进快速收缩肌肉的松弛阶段起着关键作用，可能是强选择压力的一个部位。初步数据有力地表明，来自南极鱼类的蛋白质已经被修改，以确保在低温下的功能。一套物理技术将用于确定南极鱼小蛋白对钙和镁的解离常数和离子从蛋白质解离的单向速率常数。2 .南极鱼类小白蛋白的全长cDNA克隆将有助于推断初级氨基酸序列。这些数据将有助于深入了解南极鱼类蛋白质在极低体温下发挥作用的结构要素。对心肌肌红蛋白表达模式进行广泛的调查。先前的研究表明，在南极南极南极鱼类（冰鱼科）的一个家族的心脏中，细胞内氧结合蛋白肌红蛋白（Mb）的存在或不存在的变化模式。由于Mb在表达该蛋白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异常低的生态位竞争。这导致预测类似的心肌Mb损失应该在其他南极鱼类群中观察到。该项目的这一部分将调查尽可能多的南极鱼物种中心脏Mb的存在和缺失，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缺失的机制。

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.