Immunocytochemical localization of galactosyltransferase in HeLa cells: codistribution with thiamine pyrophosphatase in trans-Golgi cisternae.
An affinity-purified, monospecific rabbit antibody against soluble human milk galactosyltransferase was used to localize the enzyme in HeLa cells by immunofluorescence and by the protein A-gold technique at the electron microscope level. Specific immunofluorescence was observed in a juxtanuclear cytoplasmic region which was identified, on immunostained thin sections of low-temperature Lowicryl K4M-embedded HeLa cells, as Golgi apparatus. Label by gold particles was limited to two to three trans cisternae of the Golgi apparatus, indicating a compartmentalization of galactosyltransferase in the cisternal stack. Combination of preembedding thiamine pyrophosphatase cytochemistry, with postembedding immunostaining for galactosyltransferase proved codistribution of the two enzymes. However, the acid phosphatase-positive, trans-most cisterna was negative for galactosyltransferase. The close topological association of both galactosyltransferase and thiamine pyrophosphatase (or nucleoside diphosphatase) suggests a concerted action of both enzymes in glycosylation.
D005455:Fluorescent Antibody Technique; D005700:Galactosyltransferases / Q000378:metabolism*; D006056:Golgi Apparatus / Q000201:enzymology* / Q000648:ultrastructure; D006367:HeLa Cells / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D008854:Microscopy, Electron; D011755:Pyrophosphatases / Q000378:metabolism*; D013834:Thiamine Pyrophosphatase / Q000378:metabolism*
D005700:Galactosyltransferases; D011755:Pyrophosphatases; D013834:Thiamine Pyrophosphatase