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Resonance Raman observation of the structural dynamics of FixL on signal transduction and ligand discrimination.
- Source :
-
Biochemistry [Biochemistry] 2007 May 22; Vol. 46 (20), pp. 6086-96. Date of Electronic Publication: 2007 May 01. - Publication Year :
- 2007
-
Abstract
- FixL is a heme-based O2 sensor protein, which responds to low O2 concentrations by activating the transcriptional activator FixJ. Signal transduction is initiated by the dissociation of O2 from the sensor domain of FixL, resulting in protein conformational changes that are transmitted to a histidine kinase domain. To gain insight into the FixL sensing mechanism, we monitored changes in the protein's structure in the picosecond to millisecond time frame, following the dissociation of the ligand using time-resolved resonance Raman spectroscopy. This study presents the time-resolved resonance Raman spectra of Sinorhizobium meliloti FixL upon O2 dissociation, as well as upon CO dissociation. The FixL spectra show that there are three steps in the dynamic structural changes that result from ligand dissociation. Ligand-dependent structural dynamics are observed in the earliest step. On the basis of comparisons of these structural changes, a scheme for the signal transduction of FixL is proposed which supports the FG loop switch mechanism. Similar spectral changes were observed both for the sensor domain and for the full-length protein, although structural changes occurred faster with the former than with the latter. This difference in rate suggests that the structural changes occurring in the heme pocket are coupled to those of the kinase domain. The implications of these results for FixL's sensing mechanism are discussed.
- Subjects :
- Bacterial Proteins metabolism
Carbon Monoxide metabolism
Heme chemistry
Hemeproteins metabolism
Histidine Kinase
Ligands
Oxygen metabolism
Protein Binding
Protein Kinase Inhibitors chemistry
Protein Kinases metabolism
Protein Structure, Tertiary
Sinorhizobium meliloti chemistry
Sinorhizobium meliloti physiology
Spectrum Analysis, Raman
Bacterial Proteins chemistry
Bacterial Proteins physiology
Hemeproteins chemistry
Hemeproteins physiology
Signal Transduction physiology
Thermodynamics
Subjects
Details
- Language :
- English
- ISSN :
- 0006-2960
- Volume :
- 46
- Issue :
- 20
- Database :
- MEDLINE
- Journal :
- Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 17469799
- Full Text :
- https://doi.org/10.1021/bi062083n