The oxygen sensing SmFixL protein from S. meliloti regulates nitrogen fixation in the root nodules of alfalfa plants. SmFixL is part of both the heme-PAS and histidine kinase families of biological sensors that regulate a wide variety of important cellular processes in nature. Oxygen binding to the Heme-PAS domain of SmFixL turns off the histidine kinase domain, regulating nitrogen fixation and microaerobic respiration in S. meliloti. The oxygen sensing mechanism of SmFixL is poorly understood. We have examined the role of several conserved Fa-helix residues in the heme domain of SmFixL* using site-directed mutagenesis, small molecule binding studies with nitric oxide and cyanide and kinase assays. Our studies with the SmFixL* protein variants Y197A, R200(A/H/E/Q), and R214A indicate that the conserved residues R200, R214 and Y197 play important roles in oxygen binding to the heme domain and may play a crucial role in signal transduction with the kinase domain. A detailed understanding of the oxygen sensing mechanism of SmFixL will lead to a better understanding of the Heme-PAS and histidine kinase families.

Conserved heme domain residues play a crucial role in the oxygen sensing mechanism of the SmFixL protein from S. meliloti

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.