Essential, Completely Conserved Glycine Residue in the Domain III S2–S3 Linker of Voltage-gated Calcium Channel α1 Subunits in Yeast and Mammals

• Published in: The Journal of biological chemistry 2007-08, Vol.282 (35), p.25659
• Main Authors: Kazuko Iida, Jinfeng Teng, Tomoko Tada, Ayaka Saka, Masumi Tamai, Hiroko Izumi-Nakaseko, Satomi Adachi-Akahane, Hidetoshi Iida
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M703757200

Voltage-gated Ca 2+ channels (VGCCs) mediate the influx of Ca 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 α 1 subunit of VGCC, CCH1 . Here, we identify a cch1 allele producing a completely nonfunctional Cch1 protein with a Gly 1265 to Glu substitution present in the domain III S2–S3 cytoplasmic linker. Comparison of amino acid sequences of this linker among 58 VGCC α 1 subunits from 17 species reveals that a Gly residue whose position corresponds to that of the Cch1 Gly 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 1265 is essential for Cch1 function because of the smallest residue volume. Replacement of the Gly 959 residue of a rat brain Ca v 1.2 α 1 subunit (rbCII), positionally corresponding to the yeast Cch1 Gly 1265 , with Glu, Ser, Lys, or Ala results in the loss of Ba 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.