The overall goal of this project is to gain a close insight into the mechanism relating to """"""""stringent control"""""""" and the extent to which it is important in the control of growth. This directs our efforts in two main directions. The first is the study of the genes responsible for the synthesis and breakdown of ppGpp, the apparent mediator of this global control system. The second direction is to understand the molecular mechanisms by which targets of stringent control are regulated. A major feature of this proposal is to elucidate the basic molecular aspects of a gene known to be involved in ppGpp metabolism, but essentially neglected for over a decade, namely the relA gene. We have been able to successfully make progress in studies related to the structure and regulation of this gene, and developed tools for interesting and significant further experiments. It is also evident that the dissection of regulatory mechanisms affecting the highly evolved ribosomal promoters, the main target of the system studied, is not a simple task. Thus, the main objective of this proposal will be dealing with structure-function relationship of the relA gene, the search for a relA independent ppGpp synthetase, and studies on the regulation of relA promoter and the regulatory consequences and structures for regulatory features of promoters that are influenced by growth conditions. This will be approached both by the isolation of mutants using a selection system that was developed in our laboratory and by comparing ribosomal promoters from different organisms.
