MOLECULAR NOVELTY AND CONSERVATION IN BACTERIAL PROTEIN SEQUENCES

从不同细菌的基因序列推导的蛋白质序列， 古细菌产生了大量关于蛋白质的新知识 功能、相互作用和进化。 研究了一些新的发现， 通过包括定向诱变的协同方法， 光谱/酶学分析和计算机序列分析 数据库。调查结果包括： a. 主要真核生物蛋白质家族的细菌同源物。 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 类似于蛋白激酶C亚家族，但它们的磷酸化 具体情况有待确认。 B。 谷氨酸脱氢酶中新的质子交换机制。 这 酶不同于其他NAD/NADP依赖性激酶， 催化性组氨酸残基。 从序列保守性和位点- 定向诱变E.大肠杆菌酶，与 共生梭菌酶的晶体结构，赖氨酸三联体 在活性位点中鉴定了残基。它们具有新颖的质子化 性质和明显的行动一致，在二羧酸底物 结合、铵的去质子化和其它质子交换步骤， 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，调查了全球 数据库序列相似性搜索。百分之50以上的普选 可分类的蛋白质序列在E.杆菌和 其他研究充分的肠道细菌，其中许多具有真核生物 同系物。 低复杂性区段和多个重复的实例是 出现的频率越来越高。 项目意义：代谢和代谢的基因组序列 形态遗传多样的细菌继续提供丰富的和成本- 分子功能新发现的有效来源， 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.