STARD7
{{Short description|Protein-coding gene in the species Homo sapiens}}
{{Infobox_gene}}
StAR-related lipid transfer domain protein 7 (STARD7) or gestational trophoblastic tumor gene-1 (GTT1) is a lipid transporter that specifically binds and transports phosphatidylcholine between membranes.{{cite journal | vauthors = Horibata Y, Sugimoto H | title = StarD7 mediates the intracellular trafficking of phosphatidylcholine to mitochondria | journal = The Journal of Biological Chemistry | volume = 285 | issue = 10 | pages = 7358–65 | date = March 2010 | pmid = 20042613 | pmc = 2844184 | doi = 10.1074/jbc.M109.056960 | doi-access = free }}
Function and tissue distribution
StarD7 is found in the cytosol and associated with the mitochondrion. When overproduced in the cell, mitochondrial levels of phosphatidylcholine rise. High levels of the protein are found in tumor cells compared to normal cells, suggesting a role in cell proliferation.{{cite journal | vauthors = Durand S, Angeletti S, Genti-Raimondi S | title = GTT1/StarD7, a novel phosphatidylcholine transfer protein-like highly expressed in gestational trophoblastic tumour: cloning and characterization | journal = Placenta | volume = 25 | issue = 1 | pages = 37–44 | date = January 2004 | pmid = 15013637 | doi = 10.1016/S0143-4004(03)00214-5 }}
Structure
There are two forms of StarD7: StarD7-I and StarD7-II. The former is 295 amino acids long. StarD7-I possesses an additional 75 amino acids at its amino-terminus, which form a signaling sequence that targets it to the outer membrane of the mitochondrion.
StarD7 contains a StAR-related transfer domain (START), from which it derives its name. Moreover, the protein is a member of the predominantly phosphatidylcholine transporter subfamily of START proteins, the StarD2 subfamily. It shares 25% sequence identity with StarD2.