Myxococcus xanthus is an excellent prokaryotic system for studying the regulation of development. M. xanthus shows a developmental cycle which is similar to the eukaryotic slime molds such as Dictyostelium discoideum. However, there are several distinct advantages to studying development in M. xanthus, since it is a simple gram-negative bacterium. We propose to study morphogenesis and the molecular mechanisms of control of gene expression during development using M. xanthus as a model system. We will continue to work on the on-going projects such as characterization of development-specific sigma factors, expression of development-specific proteins, GTP-binding proteins and msDNAs. We will also attempt to explore several new aspects of M. xanthus including protein kinases and membrane proteins associated with cell motility and morphogenesis. In this proposal, we will pursue the following specific projects: (1) Identification and characterization of development-specific sigma factors. Using the rpoD gene of M. xanthus [the gene for the vegetative sigma factor (sigA)] as a probe, we will continue to clone various development-specific sigma factors and to investigate their roles in differentiation. (2) Protein U and S. In contrast to protein S (an early developmental protein), protein U is a typical late-developmental protein. The gene for protein U and S will be carried out to elucidate how they are secreted and assembled on the spore surface. (3) GTP binding proteins and protein kinases. In addition to various GTP-binding proteins, recently we have found that M. xanthus contains a gene coding for a protein with significant sequence similarity to eukaryotic protein kinases. We will not only characterize this gene and its role in M. xanthus but also further explore to find other genes for protein kinases. (4) Characterization of the major inner membrane protein. We have found that the inner membrane fraction of M. xanthus contains a protein of 130 kd unusually in a large amount. We have recently cloned the gene for this protein and will characterize it for its possible roles in cellular motility and morphogenesis. (5) RecA proteins. We found that M. xanthus contains two recA genes. We will characterize these genes in terms of their functions in the life cycle. (6) Expression and roles of retrons-Mx65 and -Mx162. M. xanthus contains two independent retrons producing msDNA-Mx65 and msDNA-Mx162, respectively. We will further explore their roles and explore their roles and expression during the life cycle.
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