title: CO-dependent activity-controlling mechanism of heme-containing CO-sensor protein, neuronal PAS domain protein 2.
abstract: Neuronal PAS domain protein 2, which was recently established to be a heme protein, acts as a CO-dependent transcription factor. The protein consists of the basic helix-loop-helix domain and two heme-containing PAS domains (PAS-A and PAS-B). In this study, we prepared wild type and mutants of the isolated PAS-A domain and measured resonance Raman spectra of these proteins. Upon excitation of the Raman spectrum at 363.8 nm, a band assignable to Fe3+-S stretching was observed at 334 cm(-1) for the ferric wild type protein; in contrast, this band was drastically weaker in the spectrum of C170A, suggesting that Cys170 is an axial ligand of the ferric heme. The Raman spectrum of the reduced form of wild type was mainly of six-coordinate low spin, and the nu11 band, which is sensitive to the donor strength of the axial ligand, was lower than that of reduced cytochrome c3, suggesting coordination of a strong ligand and thus a deprotonated His. In the reduced forms of H119A and H171A, the five-coordinate species became more prevalent, whereas no such changes were observed for C170A, indicating that His119 and His171, but not Cys170, are axial ligands in the ferrous heme. This means that ligand replacement from Cys to His occurs upon heme reduction. The nu(Fe-CO) versus nu(C-O) correlation indicates that a neutral His is a trans ligand of CO. Our results support a mechanism in which CO binding disrupts the hydrogen bonding of His171 with surrounding amino acids, which induces conformational changes in the His171-Cys170 moiety, leading to physiological signaling.
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Myodaiji, Okazaki, Aichi 444-8787, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uchida
authors.forename: Emiko
authors.initials: E
authors.lastname: Sato
authors.forename: Akira
authors.initials: A
authors.lastname: Sato
authors.forename: Ikuko
authors.initials: I
authors.lastname: Sagami
authors.forename: Toru
authors.initials: T
authors.lastname: Shimizu
authors.forename: Teizo
authors.initials: T
authors.lastname: Kitagawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002248:Carbon Monoxide / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D003574:Cytochrome c Group / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D019281:Dimerization; D006418:Heme / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008099:Liver / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000502:physiology*; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011522:Protons; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013059:Spectrum Analysis, Raman; D013997:Time Factors; D014157:Transcription Factors / Q000737:chemistry / Q000502:physiology*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D002248:Carbon Monoxide; D003545:Cysteine; D003574:Cytochrome c Group; D004247:DNA; D006418:Heme; D006639:Histidine; D007501:Iron; D008024:Ligands; D009419:Nerve Tissue Proteins; D011522:Protons; D014157:Transcription Factors; C491259:Npas2 protein, mouse; C017165:cytochrome c(3)