MOLECULAR STUDIES OF CHEMORECEPTION

活细胞的一个基本特征是能够对特定的、 外部化学信号。就像对激素有反应的真核细胞 或神经递质，细菌含有特定的受体，暴露在 细胞表面，识别相关化合物。这些细胞是 趋化性作为多组分作用的结果， 连接感受器和鞭毛的感觉反应系统。长期的 这个实验室的目标是为详细的分子生物学做出贡献 对趋化系统的描述。最近的进展使这一点成为可能 这将是第一个被详细了解的受体系统。 越来越多的人将细菌的化学感受和 真核细胞受体系统表明，至少有一些信息 所获得的有关原核系统的信息将具有普遍意义。 这一建议涉及生理、遗传和生化方法，以 大肠埃希菌化学感受的研究。主要强调的是 致力于转导蛋白的研究，转导蛋白是一种完整的膜蛋白 趋化作用的激发和适应阶段的中枢 行为。适应涉及换能器的共价修饰， 多个谷氨酰残基上的蛋白质羧甲基化 网站。其中一些谷氨酰残基的存在是因为谷氨酸是 酶促去胺化以产生谷氨酸。功能意义 多重甲基化和去酰胺化将通过改变 人工合成寡核苷酸导向的修饰位点 诱变。换能器低聚物的模式将用 希望明确这些复合体在战术功能上的意义。 传感器的结构和构象变化将是 通过纯化蛋白质进行研究，通过使用光谱方法来 监测构象差异，并通过发展条件 这些分子可以结晶。

A basic feature of living cells is the ability to respond to specific, external chemical signals. Like eukaryotic cells that respond to hormones or neurotransmitters, bacteria contain specific receptors, exposed on the cell surface, that recognize relevant compounds. These cells are chemotactic as the result of the functioning of a multicomponent, sensory-response system that links receptors to flagella. The long-term goal of this laboratory is to contribute to a detailed molecular biological description of the chemotactic system. Recent progress makes it likely that this will be the first receptor system to be understood in detail. The growing number of analogies between bacterial chemoreception and eukaryotic receptor systems suggest that at least some of the information obtained about the prokaryotic system will have general significance. This proposal involves physiological, genetic and biochemical approaches to the study of chemoreception in Escherichia coli. Primary emphasis is placed on the study of transducers, which are integral membrane proteins central to both the excitation and adaptation phases of chemotactic behavior. Adaptation involves covalent modification of transducers, specifically protein carboxyl methylation at multiple glutamyl residue sites. Some of those glutamyl residues are present because glutamines are enzymatically deamidated to create glutamates. The functional significance of multiple methylation and deamidation will be examined by alteration of the modification sites using synthetic oligonucleotide-directed mutagenesis. The pattern of transducer oligomers will be studied with the hope of defining the significance of these complexes in tactic function. The structure and conformational changes of transducers will be investigated by purifying the proteins, by using spectroscopic methods to monitor conformational differences and by developing conditions in which the molecules can be crystallized.