The oxygen sensing SmFixL protein from S. meliloti regulates nitrogen fixation in the root nodules of alfalfa plants. SmFixL is part of the heme-PAS 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. The oxygen sensing mechanism ofSmFixL is poorly understood. We have examined the role of conserved Fa-helix residues in the heme domain of SmFixL* using site-directed mutagenesis and small molecule binding studies with kinase assays. Our results indicate that the conserved residues R200, R214 and Y197 play important roles in oxygen sensing in the heme domain and may play a crucial role in signal transduction to the kinase domain. A detailed understanding of the oxygen sensing mechasnism of SmFixL may lead to a better understanding of the Heme-PAS and histidine kinase families.

Role of conserved heme residues in the oxygen-sensing mechanism of the SmFixL protein from S. meliloti

2019 Spring National Meeting

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