FixL proteins

Sequences are available for FixL and FixJ proteins from several rhizobial species, including S. meliloti, B. japonicum, Azorhizobium caulinodans, and Rhizobium leguminosarum (9,20,21,31). As a rule, FixL proteins contain three... 

The FixL protein has a beautiful dark red color, much like blood, when it is exposed to air (Figure 7.2). When air is removed, FixL acquires a slight purple tinge. Alternatively, it becomes a bright cherry red when carbon monoxide is added to it. Such changes in the way... 

Lois, A.F. Ditta, G.S. Helinski, D.R. The oxygen sensor FixL of Rhizobium meliloti is a membrane protein containing four possible transmembrane segments. J. Bacteriol., 175, 1103-1109 (1993)... 

NifA proteins from Rhizobium and Rhodobacter share two common features they are directly inhibited by oxygen and they both possess a -Cys-X-X-X-X-Cys- motif. Oxygen sensitivity is possibly due to the binding of a metal ion by this structural motif. In Rhizobium, two gene products (FixL and FixJ) are responsible for regulating nifA expression. FixL. 

Some researchers have suggested that PAS domains are dimerization domains that regulate the activities of signal-transducing proteins by controlling their association. This is very unlikely for the photoactive yellow protein, and for the PAS domains from B. japonicum FixL, the NPHl protein, and the HERG protein, all of which crystallize as monomers (14,42,45,50). In sensor kinases of the two-component... 

Figure 4 Structure of the Bradyrhizobium japonicum FixL heme-bindiug PAS damain ( FixLH) and its close resemblance to the structure of photoactive yellow protein (PYP). On the left is a ribbons diagram showing secondary-structure elements in FixLH on the right is a comparison of the structures of FixLH (dark gray) and PYP (light gray), together with their heme and hydroxycinnamate cofactors, respectively. Consecutive letters denote consecutive regions of secondary structure. (From Ref 14.)...

Gilles-Gonzalez MA, Gonzalez G. Regulation of the kinase activity of heme protein FixL from the two-component system FixL/FixJ of Rhizobium meliloti. J Biol Chem 1993 268 16293-16297. 

Lois AF, Weinstein M, Ditta GS, Helinski DR. Autophosphorylation and phosphatase activities of the oxygen-sensing protein FixL of Rhizobium meliloti are coordinately regulated by oxygen. J Biol Chem 1993 268 4370-4375. 

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