STIM1
Encyclopedia
Stromal interaction molecule 1 is a protein
that in humans is encoded by the STIM1 gene
. STIM1 has a single transmembrane domain, and is localized to the endoplasmic reticulum
, and to a lesser extent to the plasma membrane.
Even though the protein has been identified earlier, its function was unknown until recently. In 2005, it was discovered that STIM1 functions as a calcium sensor in the endoplasmic reticulum
. Upon activation of the IP3 receptor, the calcium concentration in the endoplasmic reticulum decreases, which is sensed by STIM1, via its EF hand
domain. STIM1 activates the "store-operated" ORAI1
calcium ion channels in the plasma membrane, via protein protein interaction .
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that in humans is encoded by the STIM1 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. STIM1 has a single transmembrane domain, and is localized to the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
, and to a lesser extent to the plasma membrane.
Even though the protein has been identified earlier, its function was unknown until recently. In 2005, it was discovered that STIM1 functions as a calcium sensor in the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
. Upon activation of the IP3 receptor, the calcium concentration in the endoplasmic reticulum decreases, which is sensed by STIM1, via its EF hand
EF hand
The EF hand is a helix-loop-helix structural domain found in a large family of calcium-binding proteins. The EF-hand motif contains a helix-loop-helix topology, much like the spread thumb and forefinger of the human hand, in which the Ca2+ ions are coordinated by ligands within the loop...
domain. STIM1 activates the "store-operated" ORAI1
ORAI1
Calcium release-activated calcium channel protein 1 is a calcium selective ion channel that in humans is encoded by the ORAI1 gene. Orai1 channels play important role in the activation of T-lymphocytes. The loss of function mutation of Orai1 causes severe combined immunodeficiency in humans The...
calcium ion channels in the plasma membrane, via protein protein interaction .