MID1 is a yeast Saccharomyces cerevisiae gene encoding a plasma membrane protein required for Ca2+ influx induced by the mating pheromone, alpha-factor. Mid1 protein plays a crucial role in supplying Ca2+ during the mating process. Mid1 is composed of 548-amino-acid residues with four hydrophobic regions named H1, H2, H3 and H4, and two cysteine-rich regions (C1 and C2) at the C-terminal. This family contains the H3, H4, C1 and C2 regions. suggesting that H1 is a signal sequence responsible for the alpha-factor-induced Mid1 delivery to the plasma membrane. The region from H1 to H3 is required for the localisation of Mid1 in the plasma and ER membranes. Trafficking of Mid1-GFP to the plasma membrane is dependent on the N-glycosylation of Mid1 and the transporter protein Sec12. This findings suggests that the trafficking of Mid1-GFP to the plasma membrane requires a Sec12-dependent pathway from the ER to the Golgi, and that Mid1 is recruited via a Sec6- and Sec7-independent pathway from the Golgi to the plasma membrane.

1: Identification of functional domains of Mid1, a stretch-activated channel component, necessary for localization to the plasma membrane and Ca2+ permeation. Ozeki-Miyawaki C, Moriya Y, Tatsumi H, Iida H, Sokabe M; Exp Cell Res. 2005;311:84-95. PMID:16202999

2: Essential hydrophilic carboxyl-terminal regions including cysteine residues of the yeast stretch-activated calcium-permeable channel Mid1. Maruoka T, Nagasoe Y, Inoue S, Mori Y, Goto J, Ikeda M, Iida H; J Biol Chem. 2002;277:11645-11652. PMID:11796727

3: Phe356 in the yeast Ca2+ channel component Mid1 is a key residue for viability after exposure to alpha-factor. Tada T, Ohmori M, Iida H; Biochem Biophys Res Commun. 2004;313:752-757. PMID:14697255