title: Open and Lys-His Hexacoordinated Closed Structures of a Globin with Swapped Proximal and Distal Sites.
abstract: Globins are haem-binding proteins with a conserved fold made up of α-helices and can possess diverse properties. A putative globin-coupled sensor from Methylacidiphilum infernorum, HGbRL, contains an N-terminal globin domain whose open and closed structures reveal an untypical dimeric architecture. Helices E and F fuse into an elongated helix, resulting in a novel site-swapped globin fold made up of helices A-E, hence the distal site, from one subunit and helices F-H, the proximal site, from another. The open structure possesses a large cavity binding an imidazole molecule, while the closed structure forms a unique Lys-His hexacoordinated species, with the first turn of helix E unravelling to allow Lys52(E10) to bind to the haem. Ligand binding induces reorganization of loop CE, which is stabilized in the closed form, and helix E, triggering a large conformational movement in the open form. These provide a mechanical insight into how a signal may be relayed between the globin domain and the C-terminal domain of HGbRL, a Roadblock/LC7 domain. Comparison with HGbI, a closely related globin, further underlines the high degree of structural versatility that the globin fold is capable of, enabling it to perform a diversity of functions.
authors.affiliation: Centre for Chemical Biology, Universiti Sains Malaysia, 10 Persiaran Bukit Jambul, 11900 Bayan Lepas, Penang, Malaysia.
authors.forename: Aik-Hong
authors.initials: AH
authors.lastname: Teh
authors.affiliation: Department of Microbiology, University of Hawaii, 2538 McCarthy Mall, Honolulu, HI 96822, United States.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Saito
authors.affiliation: School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia.
authors.forename: Nazalan
authors.initials: N
authors.lastname: Najimudin
authors.affiliation: 1] Department of Microbiology, University of Hawaii, 2538 McCarthy Mall, Honolulu, HI 96822, United States [2] Advanced Studies in Genomics, Proteomics and Bioinformatics, University of Hawaii, 2565 McCarthy Mall, Honolulu, HI 96822, United States.
authors.forename: Maqsudul
authors.initials: M
authors.lastname: Alam
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D005914:Globins / Q000235:genetics / Q000648:ultrastructure*; D008958:Models, Molecular; D011485:Protein Binding; D017510:Protein Folding; D015398:Signal Transduction; D061327:Verrucomicrobia / Q000378:metabolism*
chemical_list: D005914:Globins