Mutational Pleiotropy, Epistasis, and the Adaptive Evolution of Hemoglobin Function

突变多效性、上位性和血红蛋白功能的适应性进化

• 批准号: 9594940
• 负责人: Jay Storz
• 金额: $ 34.68万
• 依托单位: UNIVERSITY OF NEBRASKA LINCOLN
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-22 至 2022-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9594940
• 关键词: Address; Allosteric Regulation; Amino Acids; Bicarbonates; Biochemical; Biology; Biophysical Process; Biophysics; Cells; Crystallization; Dimensions; Diving; Erythrocytes; Evolution; Genetic; Genetic Epistasis; Goals; Hemoglobin; Individual; Ions; Light; Medicine; Metabolic; Minor; Molecular; Molecular Evolution; Mutation; Nature; Outcome; Pathway interactions; Phenotype; Physiological; Physiology; Prevalence; Property; Protein Engineering; Proteins; Recombinants; Recording of previous events; Regulation; Research Project Grants; Resolution; Role; Site; Site-Directed Mutagenesis; Structure; System; Transfusion; Vertebrates; X-Ray Crystallography; base; combinatorial; design; experimental study; innovation; inorganic phosphate; insight; mutant; novel; oxygen transport; pleiotropism; protein function; sample fixation; structural biology

The step-by-step evolution of novel phenotypes is central to several fundamental questions in biology. In studies of novel protein functions, the problem becomes experimentally tractable if it is possible to identify and functionally characterize the complete set of causative mutations. With such a system, it is possible to address key questions: Do novel functions evolve via the successive fixation of beneficial mutations that each produce an adaptive change in phenotype when they first arise? Alternatively, are evolutionary transitions in protein function facilitated by neutral mutations that produce no adaptive benefit when they first arise, but which potentiate the function-altering effects of subsequent mutations? By reconstructing all possible mutational pathways that connect ancestral and descendant proteins it is also possible to address fundamental questions about the roles of contingency and determinism in protein evolution. For example: Can novel functions evolve from any possible ancestral starting point, or are specific evolutionary outcomes contingent on prior history? We will address these questions by experimentally dissecting the molecular basis of a key physiological innovation during vertebrate evolution. Specifically, we will examine the evolution of a unique allosteric mechanism for regulating hemoglobin (Hb) function in the red blood cells of crocodilians. This unique mode of allosteric regulatory control contributes to crocodilians’ extraordinary capacities for breath-hold diving. Using ancestral protein resurrection in conjunction with a combinatorial protein engineering approach based on site- directed mutagenesis, we will examine the effects of sequential mutational steps in the evolution of the novel allosteric mechanism of crocodilian Hb. We will also obtain insights into the structural basis of the change in Hb function, as X-ray crystallography experiments will reveal biophysical mechanisms at atomic resolution. The specific aims of the project are as follows: (1) Identify the specific mutations that are responsible for the evolution of the novel protein function, and quantify their additive and nonadditive effects; and (2) Identify and characterize the biophysical mechanisms responsible for the functional transition (gain of novel function, loss of ancestral function). In combination, accomplishing Specific Aims 1 and 2 will reveal the molecular basis of a key physiological innovation and will provide general insights into the pathways by which such innovations evolve.

新表型的分步演化对于生物学的几个基本问​​题至关重要。在 对新型蛋白质功能的研究，如果可以识别和 在功能上表征了完整的因果突变。使用这样的系统，可以解决 关键问题：做新功能通过成功的有益突变的成功固定而发展 首次出现时表型的自适应变化？另外，是蛋白质的进化过渡 首次出现时没有产生自适应益处的中性突变制备的功能，但 潜力随后突变的改变功能的影响？通过重建所有可能的突变 连接祖先和后代蛋白的途径也可以解决基本问题 关于偶然性和确定蛋白质进化的作用。例如：新功能可以演变 从任何可能的祖先起点，还是特定的进化结果取决于先前的历史？ 我们将通过实验剖析关键生理的分子基础来解决这些问题 脊椎动物进化过程中的创新。具体来说，我们将研究独特的变构的演变 调节鳄鱼红细胞中血红蛋白（Hb）功能的机制。这种独特的模式 变构调节控制有助于鳄鱼的非凡能力，以进行呼吸潜水。使用 祖先蛋白质复活与基于位点的组合蛋白工程方法结合 定向诱变，我们将检查新型突变步骤在新颖的演变中的影响 鳄鱼HB的变构机制。我们还将了解HB变化的结构基础 X射线晶体学实验的功能将在原子分辨率下揭示生物物理机制。这 该项目的具体目标如下：（1）确定负责该的特定突变 新型蛋白质功能的进化，并量化其添加剂和非添加作用； （2）识别和 表征负责功能过渡的生物物理机制（新功能的增益，损失 祖先功能）。结合起来，完成特定的目标1和2将揭示A的分子基础 关键的生理创新，并将提供有关此类创新的途径的一般见解 进化。