REGULATION OF M XANTHUS MOTILITY AND DEVELOPMENT

M Xanthus 活力和发育的调节

• 批准号: 2444845
• 负责人: PATRICIA L HARTZELL
• 金额: $ 14.04万
• 依托单位: UNIVERSITY OF IDAHO
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 1999-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2444845
• 关键词: Myxococcus; bacterial genetics; bacterial proteins; biological signal transduction; cell differentiation; cell motility; gene expression; gene mutation; genetic mapping; genetic regulation; guanine nucleotide binding protein; molecular cloning; mutant; plasmids; protein purification; spores; suppressor mutations; transcription factor

Myxococcus xanthus is a unicellular prokaryote which forms multicellular structures containing heat-resistant, differentiated spores when starved for nutrients. We propose to study MglA, a GTP-binding protein required for both the morphogenesis of this multicellular structure (a fruiting body) and the differentiation of spores but not for vegetative growth. M. xanthus is the only known prokaryote which has a protein in the family of small (20-25kDa) molecular weight ras-like G-proteins. Like its homolog, H-ras, mutations that destroy the consensus GTP-binding region of mglA abolish its activities. However, unlike all other eukaryotic G-proteins in this family, MglA is not essential. In addition to affecting morphogenesis and sporogenesis, mglA- mutations also abolish motility. Our results show that MglA interacts with MglB, the product of the co-expressed gene in its transcription unit. We have found that mglB-lacZ translational fusions block motility during development but not during growth, suggesting that MglB-MglA interactions are different during growth and development. Experiments outlined in this proposal are aimed at exploring these interactions biochemically. The mechanism of regulation by mgl is complex. mgl- mutations affect expression during development of at least four genes, defined by insertions of Tn5-lac, which may explain why mgl- mutants fail to form fruiting bodies and spores. In addition, the mglA gene is required for activation of its own expression during growth and repression of its own expression during development. Identification of the cis and trans-acting elements required for autoregulation of mgl will provide new insights into G-protein signaling. We have discovered that the sporulation defect of mglA- mutants can be rescued by SAR1, a yeast GTP-binding protein in the ras family. Hence, the inability of mglA- mutants to form heat-resistant spores cannot completely be explained by their motility defect, because SAR1 does not restore motility. It takes a second-site mutation to revert the motility defect of an M. xanthus mglA- SAR1 strain. Our proposed analysis of mutations which restore motility to this strain will provide new insights into G-protein function.

黄色粘球菌是一种单细胞原核生物， 饥饿时含有耐热的、分化的孢子的结构 来获取营养我们建议研究MglA，一种GTP结合蛋白， 对于这种多细胞结构的形态发生（一个果 体）和孢子的分化，但不为营养生长。M. xanthus是唯一已知的原核生物，其具有蛋白质的家庭 小分子量（20- 25 kDa）ras样G蛋白。就像它的同源物一样， H-ras，破坏mglA的共有GTP结合区的突变 取消其活动。然而，与所有其他真核生物中的G蛋白不同， 在这个家庭中，MglA不是必需的。 除了影响形态发生和孢子发生外，mglA-突变 也会丧失运动性。我们的研究结果表明，MglA与MglB相互作用， 共表达基因在其转录单位中的产物。我们发现 mglB-lacZ翻译融合体在发育过程中阻断运动， 而不是在生长过程中，这表明MglB-MglA相互作用是不同的 在生长和发育过程中。该提案中概述的实验是 旨在探索这些生物化学的相互作用。 mgl的调节机制是复杂的。mgl-突变影响 在发育过程中表达至少四种基因，定义为 Tn 5-lac的插入，这可以解释为什么mgl-突变体不能形成 子实体和孢子。此外，mglA基因是 在生长过程中激活其自身的表达，并抑制其自身的 发展过程中的表达。顺式和反式作用的鉴定 MGL的自动调节所需的元素将提供新的见解， G蛋白信号 我们已经发现，mglA突变体的孢子形成缺陷可以是 由SAR 1拯救，SAR 1是ras家族中的酵母GTP结合蛋白。所以 不能形成耐热孢子的mglA突变体不能完全 可以用它们的运动缺陷来解释，因为SAR 1不能恢复 能动性需要第二个位点突变来恢复 个核磁xanthus mglA-SAR 1菌株。我们提出的突变分析， 恢复这种菌株的运动性将为G蛋白提供新的见解 功能