MOLECULAR NOVELTY AND CONSERVATION IN BACTERIAL PROTEIN SEQUENCES

从不同细菌的基因序列推导出的蛋白质序列和 考古细菌正在产生丰富的蛋白质新知识 功能、相互作用和进化。对一些新发现进行了研究。 通过包括定向突变在内的协同方法， 序列的光谱/酶分析和计算机分析 数据库。调查结果包括： A.主要“真核”蛋白家族的细菌同源物。细菌 进一步研究了丝氨酸/苏氨酸蛋白激酶的同源物 在蓝藻和古细菌中。这些显然是相对的 与蛋白激酶C亚家族相似，但它们的磷酸化 特异性有待确认。 B.谷氨酸脱氢酶中新的质子交换机制。这 酶不同于其他依赖NAD/NADP的脱氢酶 一种催化组氨酸残基。从序列保护和地点- 大肠杆菌酶的定向突变，与 赖氨酸三联体共生梭菌酶的晶体结构 在活性部位检测到残基。它们有新奇的质子化 性质和在二元酸盐类基质中的明显协同作用 铵的结合、去质子化和其他质子交换步骤 谷氨酸脱氢酶催化。 C.复杂细菌中的序列家族。新序列来自 多细胞和分化细菌、链霉菌、粘球菌和 各种蓝藻和古细菌，由全球 数据库序列相似性搜索。超过50%的人 可分类的蛋白质序列在大肠杆菌和 其他研究得很好的肠道细菌，其中许多是真核细菌 同系物。低复杂性分段和多次重复的示例如下 以越来越高的频率出现。 项目的意义：来自新陈代谢和 形态多样的细菌继续提供丰富和成本- 分子功能和分子新发现的有效来源 蛋白质的进化。

Protein sequences deduced from gene sequences of diverse bacteria and archaebacteria are yielding a wealth of new knowledge on protein functions, interactions and evolution. Some novel findings were studied by concerted methods including directed mutagenesis, spectroscopic/enzymological analyses and computer analyses of sequence databases. Findings include:- A. Bacterial homologs of major "eukaryotic" protein families. Bacterial homologs of Serine/Threonine protein kinases were further investigated in cyanobacteria and archaebacteria. These are evidently relatively similar to the protein kinase C subfamily, but their phosphorylation specificity remains to be confirmed. B. Novel proton exchange mechanism in glutamate dehydrogenase. This enzyme differs from other NAD/NADP dependent dehydrogenases in lacking a catalytic histidine residue. From sequence conservation and site- directed mutagenesis of the E. coli enzyme, in comparison with the crystal structure of the Clostridium symbiosum enzyme, a triad of lysine residues was identified in the active site. These have novel protonation properties and evidently act in concert in dicarboxylate substrate binding, deprotonation of ammonium and other proton exchange steps of glutamate dehydrogenase catalysis. C. Sequence families in complex bacteria. New sequences from multicellular and differentiating bacteria, Streptomyces, Myxococcus and various cyanobacteria and archaebacteria, were investigated by global database sequence similarity searches. More than 50 percent of the classifiable protein sequences did not have counterparts in E. coli and other well-studied enteric bacteria, and many of these had eukaryotic homologs. Examples of low-complexity segments and multiple repeats are emerging with increasing frequency. Significance of project: Genome sequences from metabolically and morphogenetically diverse bacteria continue to provide a rich and cost- effective source of new discoveries on the molecular functions and evolution of proteins.