In order for bacteria to control cell cycle and developmental programs, they must be able to express the appropriate proteins at the specific time and in the specific place where they are needed. Temporal and spatial regulation of proteins are achieved through multiple, often redundant, mechanisms. We have two main areas of interest: temporal regulation of protein expression mediated by tmRNA, and mechanisms of protein localization in bacteria.
We are investigating a mechanism of translational control mediated by a very unusual small RNA, called tmRNA or SsrA RNA. tmRNA is a highly abundant RNA found in all bacteria. It alters the expression of substrate proteins by intervening during translation of the mRNA to target the nascent polypeptide for proteolysis, and to release the translating ribosomes from the mRNA. We have found that tmRNA is required for regulation of the cell cycle and development in Caulobacter crescentus, and we are using biochemical and genetic approaches to understand the molecular events which underlie the tmRNA mechanism and to understand the role of tmRNA in bacterial differentiation and physiology.
Because the tmRNA pathway is required for virulence in many pathogenic bacteria, it is an attractive target for antimicrobial drug discovery. In collaboration with the laboratory of Stephen Benkovic in the Chemistry Department, we have established methods for selecting inhibitors of the tmRNA pathway in vivo. Inhibitors of several components of the pathway have been isolated from a library of cyclic peptides produced using the SICLOPPS technology. These cyclic peptides have antibacterial activity and are lead compounds for antibiotic development.
In addition to temporal regulation, proteins are also controlled by altering their location within the cell. Several key regulatory and structural proteins have specific cellular addresses in bacteria, but it is not known how many proteins are localized in a bacterium, or how most of these proteins are targeted to the proper locations. We are using bacterial genetics and epifluorescence microscopy to identify localized proteins and to dissect the localization signals within these proteins.
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