Phylogenetic analyses of potassium channel auxiliary subunits.

Results of recent genome-sequencing projects together with advances in biochemical, molecular genetic and physiological experimentation have allowed discovery of many transport auxiliary subunits. These subunits facilitate the proper movement of substrates across cell membranes. Mutations of any of these subunits can cause catastrophic effects to the transport mechanism and cause certain genetic diseases. Auxiliary subunits of ion channels are of particular interest because of their potential to diversify the transport properties of the principal subunits. Furthermore, ion channel auxiliary subunits may function in the capacity of enhancing surface expression, allowing gating, and providing chaperone-like activities. As a result of their evolutionary histories, these proteins can be grouped exclusively by phylogenetic techniques. Many of these families are found to be restricted to a single kingdom of life while others seem to be ubiquitous. Here we report the results of systematic analyses of three families of ion channel auxiliary subunits. Some subunits contain one or more transmembrane segments while others exist only in the cytoplasm. We have also observed potential horizontal transfer across kingdoms with these auxiliary subunits. In this report, we present tabulated results of homology searches, partial multiple alignments, secondary structure analyses, and phylogenetic trees for these families.