Transmembrane Protein 55A (TMEM55A)

TMEM55A catalyzes the degradation of phosphatidylinositol 4,5-bisphosphate (PtdIns-4,5-P2) by removing the 4-phosphate.The deduced 300-amino acid protein contains a central Cx(5)R phosphatase catalytic motif and 2 transmembrane domains near its C terminus, a characteristic of lysosomal transmembrane proteins. RNA dot blot analysis detected expression in all tissues examined. Fluorescence-tagged TMEM55A localized with membrane markers of late endosomes or lysosomes.Ungewickell et al. (2005) assayed the phosphatase activity of TMEM55A synthesized in insect cells and found that it specifically catalyzed removal of the 4-phosphate from PtdIns-4,5-P2. It showed no activity toward other phosphatidylinositol substrates or inositol phosphates tested.