Please join Yale Chemistry for a thesis seminar with Jessie Mohsen, Slavoff Lab.
Title: The GndA microprotein supports ATP homeostasis in Escherichia coli during heat shock
Summary: Same-strand overlapping, or nested, open reading frames (ORFs) can optimize the information content of size-constrained viral genomes by increasing the number of proteins expressed from a limited nucleotide sequence. However, nested small open reading frames (sORFs) were previously omitted from prokaryotic and eukaryotic genome annotations. It was therefore surprising when numerous nested sORFs were recently discovered in bacteria and eukaryotes. Our case study of the GndA microprotein in Escherichia coli provides evidence of an emerging model that overlapping genes can be expressed from bacterial genomes to contribute to cellular fitness. GndA interacts with the electron transport chain and ATP synthase to support cellular fitness during heat shock by affecting intracellular NAD+/NADH ratios and ATP concentrations. GndA is conserved at the amino and nucleic acid level within some gram-negative bacterial species, is predicted to form an alpha helix indicative of membrane association, co- fractionates with the membrane, and co-immunoprecipitates with multiple subunits of inner-membrane associated complexes. In the gnd gene locus, both the canonical ORF encoding 6-phosphogluconate dehydrogenase and the nested sORF encoding GndA are important to the cell’s ability to maintain ATP homeostasis during heat shock (45 °C). In this work, disassembling a gene into its components and deciphering the conditions within which a nested sORF is expressed inform further study as to how the GndA microprotein encoded by an overlapping sORF contributes to cellular fitness during the heat shock response. Characterization of nested sORFs may therefore revise our understanding of the architecture and complexity of bacterial and eukaryotic genes.
