Calcium channels: unanswered questions

Despite decades of intensive research, many questions remain unresolved regarding the structure and function of voltage-dependent calcium channels. This review considers some of those questions: Where is the activation gate? Where are the inactivation gates? How are the voltage sensors coupled to the gates? Are bacterial K+ channels good models for the Ca2+ channel pore? Are protein-protein interactions fundamental to Ca2+ channel function? Do voltage-dependent Ca2+ channels regulate basal intracellular Ca2+? Are N and P/Q channels specialized for fast neurotransmitter release?