title: Evidence for displacements of the C-helix by CO ligation and DNA binding to CooA revealed by UV resonance Raman spectroscopy.
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.
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Sayaka
authors.initials: S
authors.lastname: Inagaki
authors.forename: Shiro
authors.initials: S
authors.lastname: Yoshioka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uchida
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Mizutani
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Aono
authors.forename: Teizo
authors.initials: T
authors.lastname: Kitagawa
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002248:Carbon Monoxide / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004583:Electrons; D006418:Heme / Q000737:chemistry; D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012247:Rhodospirillum rubrum / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013059:Spectrum Analysis, Raman; D013997:Time Factors; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism*; D014364:Tryptophan / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; C108776:CooA protein, Rhodospirillum rubrum; D006420:Hemeproteins; D008024:Ligands; D015534:Trans-Activators; D006418:Heme; D002248:Carbon Monoxide; D014364:Tryptophan; D004247:DNA; D007501:Iron