2CMN

A Proximal Arginine Residue in the Switching Mechanism of the FixL Oxygen Sensor

Summary for 2CMN

• Entry DOI: 10.2210/pdb2cmn/pdb
• Related: 1DP6 1DP8 1DP9 1DRM 1LSV 1LSW 1LSX 1LT0 1XJ2 1XJ3 1XJ4 1XJ6 1Y28
• Descriptor: SENSOR PROTEIN FIXL, PROTOPORPHYRIN IX CONTAINING FE (3 entities in total)
• Functional Keywords: sensory transduction, two- component system, transmembrane, inner membrane, nitrogen fixation, transferase
• Biological source: BRADYRHIZOBIUM JAPONICUM
• Total number of polymer chains: 1
• Total formula weight: 15319.03

Authors

Gilles-Gonzalez, M.-A.,Caceres, A.I.,Silva Sousa, E.H.,Tomchick, D.R.,Brautigam, C.A.,Gonzalez, C.,Machius, M. (deposition date: 2006-05-11, release date: 2007-05-15, Last modification date: 2023-12-13)

Primary citation

Gilles-Gonzalez, M.-A.,Caceres, A.I.,Silva Sousa, E.H.,Tomchick, D.R.,Brautigam, C.A.,Gonzalez, C.,Machius, M.
A Proximal Arginine R206 Participates in Switching of the Bradyrhizobium Japonicum Fixl Oxygen Sensor
J.Mol.Biol., 360:80-, 2006

PubMed Abstract: In oxygen-sensing PAS domains, a conserved polar residue on the proximal side of the heme cofactor, usually arginine or histidine, interacts alternately with the protein in the "on-state" or the heme edge in the "off-state" but does not contact the bound ligand directly. We assessed the contributions of this residue in Bradyrhizobium japonicum FixL by determining the effects of an R206A substitution on the heme-PAS structure, ligand affinity, and regulatory capacity. The crystal structures of the unliganded forms of the R206A and wild-type BjFixL heme-PAS domains were similar, except for a more ruffled porphyrin ring in R206A BjFixL and a relaxation of the H214 residue and heme propionate 7 due to their lost interactions. The oxygen affinity of R206A BjFixL (Kd approximately 350 microM) was 2.5 times lower than that of BjFixL, and this was due to a higher off-rate constant for the R206A variant. The enzymatic activities of the unliganded "on-state" forms, either deoxy or met-R206A BjFixL, were comparable to each other and slightly lower (twofold less) than those of the corresponding BjFixL species. The most striking difference between the two proteins was in the enzymatic activities of the liganded "off-state" forms. In particular, saturation with a regulatory ligand (the Fe(III) form with cyanide) caused a >2000-fold inhibition of the BjFixL phosphorylation of BjFixJ, but a 140-fold inhibition of this catalytic activity in R206A BjFixL. Thus, in oxygen-sensing PAS domains, the interactions of polar residues with the heme edge couple the heme-binding domain to a transmitter during signal transduction.

PubMed: 16813836
DOI: 10.1016/J.JMB.2006.04.054

Experimental method

X-RAY DIFFRACTION (2.3 Å)