Essential, Completely Conserved Glycine Residue in the Domain III S2-S3 Linker of Voltage-gated Calcium Channel alpha sub(1) Subunits in Yeast and Mammals

• Published in: The Journal of biological chemistry 2007-08, Vol.282 (35), p.25659-25667
• Main Authors: Iida, Kazuko, Teng, Jinfeng, Tada, Tomoko, Saka, Ayaka, Tamai, Masumi, Izumi-Nakaseko, Hiroko, Adachi-Akahane, Satomi, Iida, Hidetoshi
• Format: Article
• Language: English
• Subjects: Saccharomyces cerevisiae
• ISSN: 0021-9258; 1083-351X

Voltage-gated Ca super(2+) channels (VGCCs) mediate the influx of Ca super(2+) that regulates many cellular events, and mutations in VGCC genes cause serious hereditary diseases in mammals. The yeast Saccharomyces cerevisiae has only one gene encoding the putative pore-forming alpha sub(1) subunit of VGCC, CCH1. Here, we identify a cch1 allele producing a completely nonfunctional Cch1 protein with a Gly super(1265) to Glu substitution present in the domain III S2-S3 cytoplasmic linker. Comparison of amino acid sequences of this linker among 58 VGCC alpha sub(1) subunits from 17 species reveals that a Gly residue whose position corresponds to that of the Cch1 Gly super(1265) is completely conserved from yeasts to humans. Systematic amino acid substitution analysis using 10 amino acids with different chemical and structural properties indicates that the Gly super(1265) is essential for Cch1 function because of the smallest residue volume. Replacement of the Gly super(959) residue of a rat brain Ca sub(v)1.2 alpha sub(1) subunit (rbCII), positionally corresponding to the yeast Cch1 Gly super(1265), with Glu, Ser, Lys, or Ala results in the loss of Ba super(2+) currents, as revealed by the patch clamp method. These results suggest that the Gly residue in the domain III S2-S3 linker is functionally indispensable from yeasts to mammals. Because the Gly residue has never been studied in any VGCC, these findings provide new insights into the structure-function relationships of VGCCs.