title: Structural insights into the coordination of iron by Thermus thermophilus HB8 ferric binding protein A.
abstract: The ferric binding protein belongs to the substrate-binding protein super-family and transports ferric ions across the periplasmic space in gram negative bacteria. This process involves the binding and release of ferric ions through conformational changes of the ferric binding protein, and the assistance of a synergistic anion. Here we report the crystal structure of Thermus thermophilus HB8's (TtFbpA) ferric binding protein A in four different forms, which represent the apo state (apo-TtFbpA), the carbonate-bound state (TtFbpACO3),and the iron- and carbonate-bound state (TtFbpAFeCO3). The ferric ion in TtFbpAFeCO3 is bound by three tyrosine residues from TtFbpA and one synergistic carbonate ion. Structural comparisons among the three different states reveal the molecular mechanisms of iron-binding by TtFbpA. Our results, together with previous studies on other bacterial periplasmic ferric binding proteins, provide a complete understanding of the structural basis for iron binding and release in the periplasm of gram-negative bacteria.
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Lu
authors.forename: Qiyun
authors.initials: Q
authors.lastname: Zhou
authors.forename: Xinquan
authors.initials: X
authors.lastname: Wang
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Liu
mesh_terms: D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002254:Carbonates / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D033902:Periplasmic Binding Proteins / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001059:Apoproteins; D001426:Bacterial Proteins; D002254:Carbonates; D033862:Iron-Binding Proteins; D033902:Periplasmic Binding Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D007501:Iron