KIN RECOGNITION BETWEEN MEDIAL GOLGI ENZYMES IN HELA-CELLS

The medial Golgi enzymes, N-acetylglucosaminyltransferase I (NAGT I) a nd mannosidase II (Mann II), and the trans Golgi enzyme, beta-1,4-gala ctosyltransferase (GalT) were each retained in the endoplasmic reticul um (ER) by grafting on the cytoplasmic tail of the p33 invariant chain . Transient and stable expression of p33/NAGT I in HeLa cells caused r elocation of endogenous Mann II to the ER and transient expression of p33/Mann II had a similar effect on endogenous NAGT I. Neither of thes e endogenous medial enzymes were affected by transient expression of p 33/GalT. These data provide strong evidence for kin recognition betwee n medial Golgi enzymes and suggest a role for them in the organization of the Golgi stack.