Roles of E. coli DedA proteins in lipid synthesis and cell division

Louisiana State University, Baton Rouge LA

Investigators

Abstract

Intellectual Merit Membrane proteins constitute 25-30% of the predicted proteins encoded in all genomes so far sequenced. However, even in a well-characterized organism such as Escherichia coli, the functions of nearly half of the predicted membrane proteins are only poorly understood. By the use of genetics to isolate novel mutants, the laboratory has acquired the tools to understand the roles of a previously uncharacterized but widely distributed and conserved gene family in lipid biosynthesis and cell division, the dedA family. DedA is a large family of inner membrane proteins found widespread in eubacteria and some Archaea. Genes for these proteins are also present in the genomes of certain green algae but have not been identified in other eukaryotic genomes. Currently, there are more than 1000 genes in the online database annotated as being dedA family members or possessing significant amino acid identity to E. coli DedA. To date, no function has been assigned to the DedA protein family. This is due largely to the inability to study the proteins genetically, as each single deletion mutant that has been made in E. coli is without an observable phenotype. A new temperature sensitive mutant, BC202, with alterations in membrane phospholipid composition and defects in cell division was isolated. BC202 has targeted deletions of two related dedA family genes (yqjA and yghB) and growth is restored by expression of either of these genes. YqjA and YghB have 61% amino acid identity so the proteins are expected to have redundant functions. BC202 is a powerful tool to study the roles of lipids in bacterial cell division and the functions of the conserved DedA superfamily of membrane proteins. The specific aims of this project are (1) to determine the lipid and cell division defects in the yghB, ygiA double mutant; (2) to determine the function(s) of YghB and YqjA; and (3) to determine the functional conservation of DedA family members from divergent bacterial species. Broader Impacts Results from the project will lead to a deeper understanding of the roles of lipids in both prokaryotic and eukaryotic cells. In an effort to enhance scientific and technological understanding, the results from these studies will be promptly published in peer-reviewed scientific journals. Materials obtained, including cloned genes and bacterial mutants will be made available for broad dissemination free of charge. The PI is keenly aware of the need to promote teaching and training of graduate and undergraduate students and will train students in the research laboratory and also will integrate the research in instruction by including aspects of the project in his teaching assignment in Microbial Physiology. The PI is also committed to broadening participation to include members from underrepresented groups in biology in his research. The PI maintains an ethnically diverse laboratory and coordinates collaborations with faculty and student researchers from Louisiana State University and Southern University.