title: The structure of a bacterial DUF199/WhiA protein: domestication of an invasive endonuclease.
abstract: Proteins of the DUF199 family, present in all Gram-positive bacteria and best characterized by the WhiA sporulation control factor in Streptomyces coelicolor, are thought to act as genetic regulators. The crystal structure of the DUF199/WhiA protein from Thermatoga maritima demonstrates that these proteins possess a bipartite structure, in which a degenerate N-terminal LAGLIDADG homing endonuclease (LHE) scaffold is tethered to a C-terminal helix-turn-helix (HTH) domain. The LHE domain has lost those residues critical for metal binding and catalysis, and also displays an extensively altered DNA-binding surface as compared with homing endonucleases. The HTH domain most closely resembles related regions of several bacterial sigma70 factors that bind the -35 regions of bacterial promoters. The structure illustrates how an invasive element might be transformed during evolution into a larger assemblage of protein folds that can participate in the regulation of a complex biological pathway.
authors.affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., Seattle, WA 98006, USA.
authors.forename: Brett K
authors.initials: BK
authors.lastname: Kaiser
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Clifton
authors.forename: Betty W
authors.initials: BW
authors.lastname: Shen
authors.forename: Barry L
authors.initials: BL
authors.lastname: Stoddard
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D004720:Endonucleases / Q000737:chemistry* / Q000378:metabolism; D019077:Helix-Turn-Helix Motifs; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013171:Spores, Bacterial / Q000378:metabolism; D020124:Thermotoga maritima / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004720:Endonucleases