Figure 1

A. Multiple alignment of selected representatives of the OST-HTH superfamily. The consensus shown below was computed on a complete alignment of the superfamily which included 256 non-redundant versions of domain and was used to color columns of the alignment. The consensus positions are labeled thus: h- hydrophobic, l- aliphatic, s-small and p-polar. The proteins are labeled with the protein name followed by the organism abbreviation and Genbank Gi number delimited by underscores. The organism abbreviations are: Anid: Aspergillus nidulans; Atha: Arabidopsis thaliana; Bjap: Bradyrhizobium japonicum; Bthe: Bacteroides thetaiotaomicron; Ccur: Cryptobacterium curtum; Cele: Caenorhabditis elegans; Chut: Cytophaga hutchinsonii; Cjej: Campylobacter jejuni; Cpar: Cryptosporidium parvum; Daro: Dechloromonas aromatica; Dmel: Drosophila melanogaster; Hsap: Homo sapiens; Mbur: Methanococcoides burtonii; Neur: nitrosomonas europaea; Nvec: Nematostella vectensis; Oter: Opitutus terrae; Pfal: Plasmodium falciparum; Pmar: Perkinsus marinus; Psyr: Pseudomonas syringae; Ptet: Paramecium tetraurelia; Rpal: Rhodopseudomonas palustris; Rsph: Rhodobacter sphaeroides; Ssp: Synechocystis sp.; Tann: Theileria annulata; Tpal: Treponema pallidum; Tpar: Theileria parva; Tthe: Tetrahymena thermophila; Xaxo: Xanthomonas axonopodis; Osat: Oryza sativa; Vvin: Vitis vinifera; Jant: Jonquetella anthropi; Pinf: Phytophthora infestans. B. The average NMR structure of the OST-HTH domain from the protein NE0665 (2 kpm) is rendered as a cartoon with the helices and strands labeled as per the secondary structure progression. The regions inferred to potentially contact dsRNA based on the superposition to the archaeal CDC6-DNA co-crystal structure are indicated. The region of the OST-HTH that is circled is the unique insert that distinguishes it from other wHTH domains.