title: Evolutionary analyses of KCNQ1 and HERG voltage-gated potassium channel sequences reveal location-specific susceptibility and augmented chemical severities of arrhythmogenic mutations.
abstract: BACKGROUND
  Mutations in HERG and KCNQ1 potassium channels have been associated with Long QT syndrome and atrial fibrillation, and more recently with sudden infant death syndrome and sudden unexplained death. In other proteins, disease-associated amino acid mutations have been analyzed according to the chemical severity of the changes and the locations of the altered amino acids according to their conservation over metazoan evolution. Here, we present the first such analysis of arrhythmia-associated mutations (AAMs) in the HERG and KCNQ1 potassium channels.
  
  
  RESULTS
  Using evolutionary analyses, AAMs in HERG and KCNQ1 were preferentially found at evolutionarily conserved sites and unevenly distributed among functionally conserved domains. Non-synonymous single nucleotide polymorphisms (nsSNPs) are under-represented at evolutionarily conserved sites in HERG, but distribute randomly in KCNQ1. AAMs are chemically more severe, according to Grantham's Scale, than changes observed in evolution and their severity correlates with the expected chemical severity of the involved codon. Expected chemical severity of a given amino acid also correlates with its relative contribution to arrhythmias. At evolutionarily variable sites, the chemical severity of the changes is also correlated with the expected chemical severity of the involved codon.
  
  
  CONCLUSIONS
  Unlike nsSNPs, AAMs preferentially locate to evolutionarily conserved, and functionally important, sites and regions within HERG and KCNQ1, and are chemically more severe than changes which occur in evolution. Expected chemical severity may contribute to the overrepresentation of certain residues in AAMs, as well as to evolutionary change.
authors.affiliation: Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada. hajacks@interchange.ubc.ca
authors.forename: Heather A
authors.initials: HA
authors.lastname: Jackson
authors.forename: Eric A
authors.initials: EA
authors.lastname: Accili
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000235:genetics*; D003062:Codon; D017124:Conserved Sequence; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics*; D019143:Evolution, Molecular; D006801:Humans; D009154:Mutation / Q000235:genetics*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics
chemical_list: D003062:Codon; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C485621:KCNQ1OT1 long non-coding RNA, human; D024642:Potassium Channels, Voltage-Gated