Evidence for displacements of the C-helix by CO ligation and DNA binding to CooA revealed by UV resonance Raman spectroscopy.
J Biol Chem
; 281(16): 11271-8, 2006 Apr 21.
Article
in En
| MEDLINE
| ID: mdl-16439368
ABSTRACT
The UV and visible resonance Raman spectra are reported for CooA from Rhodospirillum rubrum, which is a transcriptional regulator activated by growth in a CO atmosphere. CO binding to heme in its sensor domain causes rearrangement of its DNA-binding domain, allowing binding of DNA with a specific sequence. The sensor and DNA-binding domains are linked by a hinge region that follows a long C-helix. UV resonance Raman bands arising from Trp-110 in the C-helix revealed local movement around Trp-110 upon CO binding. The indole side chain of Trp-110, which is exposed to solvent in the CO-free ferrous state, becomes buried in the CO-bound state with a slight change in its orientation but maintains a hydrogen bond with a water molecule at the indole nitrogen. This is the first experimental data supporting a previously proposed model involving displacement of the C-helix and heme sliding. The UV resonance Raman spectra for the CooA-DNA complex indicated that binding of DNA to CooA induces a further displacement of the C-helix in the same direction during transition to the complete active conformation. The Fe-CO and C-O stretching bands showed frequency shifts upon DNA binding, but the Fe-His stretching band did not. Moreover, CO-geminate recombination was more efficient in the DNA-bound state. These results suggest that the C-helix displacement in the DNA-bound form causes the CO binding pocket to narrow and become more negative.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Spectrophotometry, Ultraviolet
/
Bacterial Proteins
/
DNA
/
Trans-Activators
/
Hemeproteins
Type of study:
Prognostic_studies
Language:
En
Journal:
J Biol Chem
Year:
2006
Document type:
Article
Affiliation country:
Japón