Family 1.A.16 - The Yeast Stretch Activated Ca2+ Channel (Mid1)
Family
Family ID: 53368
The Mid1 protein of Saccharomyces cerevisiae mediates Ca2+ influx
in response to mechanical stimuli, and these responses are observed
when Mid1 is produced in Chinese hamster ovary cells. The channel
is inhibited by gadolinium, a blocker of stretch-activated cation
channels. Such stretch-activated cation channels are believed
to mediate responses to touch and hearing in animals, touch and
gravity in plants, and sensing of osmotic changes in microorganisms.
Ca2+ influx via the Mid1 channel of S. cerevisiae
is stimulated by the presence of mating pheromone. A null mutation
in the MID1 gene results in cell death upon pheromone stimulation,
possibly due to the lack of cytoplasmic Ca2+.
Mid1 is 541
aas long and exhibits a single putative TMS at residues 7-23.
The small N-terminus is probably in the cytoplasm while the large
C-terminus is in the extracytoplasmic space. It contains many
potential sites of glycosylation. Its only homologue in the current
databases is an S. pombe homologue (486 aas; spQ10063). This latter
protein has two putative TMSs at positions 12-32 and 405-485.
Sequence similarity between these two proteins are observed in
the large extracellular loop.
