Abstract

Cytosolic sulfotransferases were first isolated from the hepatic cytosol, and they have been localized in the cytoplasm of formaldehyde-fixed human cell samples. The current work was carried out to determine the subcellular localization and molecular mobility of cytosolic sulfotransferases in living human embryonic kidney (HEK) 293 cells. In this work, the subcellular location of human cytosolic sulfotransferase 1C1 (SULT1C1) was studied in cultured HEK293 cells using confocal laser-scanning microscopy. A green fluorescent protein (GFP)-tagged SULT1C1 protein was localized in the cytoplasm of living HEK293 cells. This is consistent with results from previous studies on several other cytosolic sulfotransferase isoforms. Fluorescence recovery after photobleaching microscopy was performed to assess the molecular mobility of the expressed GFP-SULT1C1 molecules. The results suggested that the expressed recombinant GFP-SULT1C1 molecules in living HEK293 cells may include both mobile and immobile populations. To obtain additional insights into the subcellular location of SULT1C1, two machine learning algorithms, Sequential Minimal Optimization and Multilayer Perceptron, were used to compute the probability distribution for the localization of SULT1C1 in nine selected cellular compartments. The resulting probability distribution suggested that the most likely subcellular location of SULT1C1 is the cytosol.