User:WafflesOnIce/Zinc transporter SLC39A7

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Zinc transporter SLC39A7 (ZIP7), also known as solute carrier family 39 member 7, is a transmembrane protein that in humans is encoded by the SLC39A7 gene.   It belongs to the ZIP family, which consists of 14 proteins that transport zinc into the cytoplasm. Its structure consists of helices that bind to zinc in a binuclear metal center. It's primary role is to control the transport of zinc from the ER and Golgi apparatus to the cytoplasm. It also plays a role in glucose metabolism. Its fruit fly orthologue is Catsup.

Structure
There are no experimentally solved structures of ZIP7 in its entirety. ZIP7 has an predicted AlphaFold structure. ZIP7, like other ZIP proteins, has eight transmembrane (TM) helices with a binuclear metal center. Two zinc ions bind to residues on TM4 (His329, Asn330, and Asp333) and TM5 (His358, Glu395, and His362). ZIP proteins are known to make homo- or heterodimeric complexes. The specific mode of transport zinc takes through ZIP transporters has not yet been determined.

Function
Zinc is an essential cofactor for more than 50 classes of enzymes. It is involved in protein, nucleic acid, carbohydrate, and lipid metabolism, as well as in the control of gene transcription, growth, development, and differentiation. Zinc cannot passively diffuse across cell membranes and requires specific transporters, such as SLC39A7, to enter the cytosol from both the extracellular environment and from intracellular storage compartments. The presence of zinc regulates the expression of ZIP transporters.

ZIP7 is a membrane transport protein of the endoplasmic reticulum. Phosphorylation of ZIP7 by casein kinase 2 stimulates the release of zinc ions from the endoplasmic reticulum. This provides a signal transduction pathway by which activation of cell surface receptors such as the epidermal growth factor receptor can regulate the activity of downstream phosphatases and kinases. ZIP7 is responsible for maintaining zinc homeostasis in the ER. Due to it's key role in several signaling pathways, the loss of ZIP7 results in an accumulation in the endoplasmic reticulum and cause ER stress.

ZIP7 is involved in controlling glucose metabolism in the skeletal muscle cells by affecting the insulin signaling pathway. Reduced expression in glucose metabolism genes and proteins such as Glut4, IRS1, IRS2, and Akt phosphorylation occur when ZIP7 mRNA is downregulated. When zinc released from ZIP7 binds to PTP1B, the insulin signaling pathway is activated.