Photoacoustic Calorimetry Studies of O₂-Sensing FixL and (R200, I209) Variants from Sinorhizobium meliloti Reveal Conformational Changes Coupled to Ligand Photodissociation from the Heme-PAS Domain.

ABSTRACT: FixL is an oxygen-sensing heme-PAS protein that regulates nitrogen fixation in the root nodules of plants. In this paper, we present the first photothermal studies of the full-length wild-type FixL protein from Sinorhizobium meliloti and the first thermodynamic profile of a full-length heme-PAS protein. Photoacoustic calorimetry studies reveal a quadriphasic relaxation for SmFixL*WT and the five variant proteins (SmFixL*R200H, SmFixL*R200Q, SmFixL*R200E, SmFixL*R200A, and SmFixL*I209M) with four intermediates from <20 ns to ∼1.5 μs associated with the photodissociation of CO from the heme. The altered thermodynamic profiles of the full-length SmFixL* variant proteins confirm that the conserved heme domain residues R200 and I209 are im

SUBMITTER: Mokdad A 

PROVIDER: S-EPMC10765370 | biostudies-literature | 2024 Jan

REPOSITORIES: biostudies-literature