title: HisE11 and HisF8 provide bis-histidyl heme hexa-coordination in the globin domain of Geobacter sulfurreducens globin-coupled sensor.
abstract: Among heme-based sensors, recent phylogenomic and sequence analyses have identified 34 globin coupled sensors (GCS), to which an aerotactic or gene-regulating function has been tentatively ascribed. Here, the structural and biochemical characterization of the globin domain of the GCS from Geobacter sulfurreducens (GsGCS(162)) is reported. A combination of X-ray crystallography (crystal structure at 1.5 A resolution), UV-vis and resonance Raman spectroscopy reveals the ferric GsGCS(162) as an example of bis-histidyl hexa-coordinated GCS. In contrast to the known hexa-coordinated globins, the distal heme-coordination in ferric GsGCS(162) is provided by a His residue unexpectedly located at the E11 topological site. Furthermore, UV-vis and resonance Raman spectroscopy indicated that ferrous deoxygenated GsGCS(162) is a penta-/hexa-coordinated mixture, and the heme hexa-to-penta-coordination transition does not represent a rate-limiting step for carbonylation kinetics. Lastly, electron paramagnetic resonance indicates that ferrous nitrosylated GsGCS(162) is a penta-coordinated species, where the proximal HisF8-Fe bond is severed.
authors.affiliation: Department of Physics, CNISM and Center for Excellence in Biomedical Research, University of Genova, Via Dodecaneso, 33, I-16146 Genova, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pesce
authors.forename: Liesbet
authors.initials: L
authors.lastname: Thijs
authors.forename: Marco
authors.initials: M
authors.lastname: Nardini
authors.forename: Filip
authors.initials: F
authors.lastname: Desmet
authors.forename: Lorenza
authors.initials: L
authors.lastname: Sisinni
authors.forename: Louise
authors.initials: L
authors.lastname: Gourlay
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bolli
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Coletta
authors.forename: Sabine
authors.initials: S
authors.lastname: Van Doorslaer
authors.forename: Xuehua
authors.initials: X
authors.lastname: Wan
authors.forename: Maqsudul
authors.initials: M
authors.lastname: Alam
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
authors.forename: Luc
authors.initials: L
authors.lastname: Moens
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.forename: Sylvia
authors.initials: S
authors.lastname: Dewilde
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D030562:Databases, Protein; D004578:Electron Spin Resonance Spectroscopy; D045302:Geobacter / Q000378:metabolism*; D005914:Globins / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006639:Histidine / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D013059:Spectrum Analysis, Raman
chemical_list: D001426:Bacterial Proteins; D006418:Heme; D006639:Histidine; D005914:Globins