K+ channel principal subunits are by far the largest and most diverse of the ion channels. This diversity originates partly from the large number of genes coding for K+ channel principal subunits, but also from other processes such as alternative splicing, generating multiple mRNA transcripts from a single gene, heteromeric assembly of different principal subunits, as well as possible RNA editing and posttranslational modifications. In this chapter, we attempt to give an overview (mostly in tabular format) of the different genes coding for K+ channel principal and accessory subunits and their genealogical relationships. We discuss the possible correlation of different principal subunits with native K+ channels, the biophysical and pharmacological properties of channels formed when principal subunits are expressed in heterologous expression systems, and their patterns of tissue expression. In addition, we devote a section to describing how diversity of K+ channels can be conferred by heteromultimer formation, accessory subunits, alternative splicing, RNA editing and posttranslational modifications. We trust that this collection of facts will be of use to those attempting to compare the properties of new subunits to the properties of others already known or to those interested in a comparison between native channels and cloned candidates.

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A common feature of animal circadian clocks is the progressive phosphorylation of PERIOD (PER) proteins, which is highly dependent on casein kinase I␦/ (CKI␦/; termed DOUBLETIME [DBT] in Drosophila) and ultimately leads to the rapid degradation of hyperphosphorylated isoforms via a mechanism involving the F-box protein, ␤-TrCP (SLIMB in Drosophila). Here we use the Drosophila melanogaster model system, and show that a key step in controlling the speed of the clock is phosphorylation of an N-terminal Ser (S47) by DBT, which collaborates with other nearby phosphorylated residues to generate a high-affinity atypical SLIMB-binding site on PER. DBT-dependent increases in the phospho-occupancy of S47 are temporally gated, dependent on the centrally located DBT docking site on PER and partially counterbalanced by protein phosphatase activity. We propose that the gradual DBT-mediated phosphorylation of a nonconsensus SLIMB-binding site establishes a temporal threshold for when in a daily cycle the majority of PER proteins are tagged for rapid degradation. Surprisingly, most of the hyperphosphorylation is unrelated to direct effects on PER stability. We also use mass spectrometry to map phosphorylation sites on PER, leading to the identification of a number of "phospho-clusters" that explain several of the classic per mutants.[Keywords: Circadian rhythms; Drosophila; PER; ␤-TrCP/SLIMB; CK1/DBT; F-box protein; phosphorylation] Supplemental material is available at http://www.genesdev.org.

We performed a genealogical analysis of the ionotropic glutamate receptor (iGluR) gene family, which includes the animal iGluRs and the newly isolated glutamate receptor-like genes (GLR) of plants discovered in Arabidopsis. Distance measures firmly placed the plant GLR genes within the iGluR clade as opposed to other ion channel clades and indicated that iGluRs may be a primitive signaling mechanism that predated the divergence of animals and plants. Moreover, phylogenetic analyses using both parsimony and neighbor joining indicated that the divergence of animal iGluRs and plant GLR genes predated the divergence of iGluR subtypes (NMDA vs. AMPA/KA) in animals. By estimating the congruence of the various glutamate receptor gene regions, we showed that the different functional domains, including the two ligand-binding domains and the transmembrane regions, have coevolved, suggesting that they assembled together before plants and animals diverged. Based on residue conservation and divergence as well as positions of residues with respect to functional domains of iGluR proteins, we attempted to examine structure-function relationships. This analysis defined M3 as the most highly conserved transmembrane domain and identified potential functionally important conserved residues whose function can be examined in future studies.

In our recent paper on the phylogeny of aculeate Hymenoptera, we supplemented our primary data set with publicly available genome sequence data from four bee species, three ant species, and one wasp species. However, we did not give detailed citations for these data, nor did we make a clear distinction between those species whose genomes had been formally published and those for which data had been made publicly available prior to publication. The published genomes were those of the wasp Nasonia vitripennis [1], the honeybee Apis mellifera [2], and the ants Harpegnathos saltator [3], Pogonomyrmex barbatus [4], and Linepithema humile [5]. The prepublication genome data came from the bees Lasioglossum albipes (NCBI Sequence Read Archive SRR578269, as part of the Lasioglossum albipes WGS project, http://www.ncbi.nlm.nih.gov/ bioproject/174755), Megachile rotundata (NCBI Protein database search, with data coming mostly from the Megachile genome sequencing project, http://www.ncbi.nlm.nih.gov/bioproject/66515), and Bombus terrestris (protein set from NCBI RefSeq and Genome Annotation projects, derived from genomic sequence generated by the Bumble Bee Genome Project, https://www. hgsc.bcm.edu/arthropods/bumble-bee-genome-project).We apologize for any confusion created by the lack of explicit citations of these data sources.