Domain architecture, predicted operons and contextual information map for CYTH domains Proteins are represented by their gene names, species abbreviations and gi as in Fig. 1. Operons are shown with genes represented as box-arrows. The contextual map shows different types of associations between the domains. Unidirectional black arrows represent domains co-occuring in the same protein. Bidirectional red arrows represent domains co-occuring in operons, the dotted red arrow represents adjacent gene transcribed in opposite directions, and the green arrow represents an experimentally derived functional association. Domain abbreviations: GuK, Guanylate kinase, NuK, Nucleotide kinase, TK, Thymidylate kinase.