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sapM

Gene
sapM
Protein
Phosphatidylinositol-3-phosphatase
Organism
Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv)
Length
299 amino acids
Function
Virulence factor that plays an important role in blocking phagosome-lysosome fusion and thus participates in the intracellular survival of the pathogen (PubMed:15753315, PubMed:23923000). Acts as a phosphatase that dephosphorylates phosphatidylinositol 3-phosphate (PI3P), a membrane trafficking regulatory lipid essential for phagosomal acquisition of lysosomal constituents (PubMed:15753315). Therefore, SapM eliminates PI3P from the phagosomal membrane by catalyzing its hydrolysis, and thus contributes to inhibition of phagosome maturation (PubMed:15753315). Also interferes with autophagy: SapM blocks autophagosome-lysosome fusion in macrophages by binding to the small GTPase RAB7, which prevents RAB7 from being involved in this process and thus negatively regulates autophagy flux (PubMed:25896765). In vitro, displays phosphatase activity with broad specificity; can dephosphorylate a variety of phosphoester substrates, with the highest activity against phosphoenolpyruvate, glycerophosphate, GTP, NADPH, phosphotyrosine and trehalose-6-phosphate (PubMed:11073936). In contrast, the enzyme exhibits poor activity against glucose-6-phosphate, phosphothreonine, and a number of nucleotides (NADP, ATP, AMP, and GMP) (PubMed:11073936).
Mass
31.807 kDa
Sequence
MLRGIQALSRPLTRVYRALAVIGVLAASLLASWVGAVPQVGLAASALPTFAHVVIVVEENRSQAAIIGNKSAPFINSLAANGAMMAQAFAETHPSEPNYLALFAGNTFGLTKNTCPVNGGALPNLGSELLSAGYTFMGFAEDLPAVGSTVCSAGKYARKHVPWVNFSNVPTTLSVPFSAFPKPQNYPGLPTVSFVIPNADNDMHDGSIAQGDAWLNRHLSAYANWAKTNNSLLVVTWDEDDGSSRNQIPTVFYGAHVRPGTYNETISHYNVLSTLEQIYGLPKTGYATNAPPITDIWGD