Ca_v1.2 I-II linker structure and Timothy syndrome

Ca_v channels are multi-subunit protein complexes that enable inward cellular Ca²⁺ currents in response to membrane depolarization. We recently described structure-function studies of the intracellular α1 subunit domain I-II linker, directly downstream of domain IS6. The results show the extent of the linker's helical structure to be subfamily dependent, as dictated by highly conserved primary sequence differences. Moreover, the difference in structure confers different biophysical properties, particularly the extent and kinetics of voltage and calcium-dependent inactivation. Timothy syndrome is a human genetic disorder due to mutations in the Ca_V1.2 gene. Here, we explored whether perturbation of the I-II linker helical structure might provide a mechanistic explanation for a Timothy syndrome mutant's (human Ca_V1.2 G406R equivalent) biophysical effects on inactivation and activation. The results are equivocal, suggesting that a full mechanistic explanation for this Timothy syndrome mutation requires further investigation.