The transmembrane domain of N-glucosaminyltransferase I contains a Golgi retention signal

Abstract

The enzyme N-acetylglucosaminyltransferase I (NT, EC 2.4.1.101) is a resident type II transmembrane protein of the Golgi apparatus. To delineate the portion of its primary sequence that is responsible for the Golgi retention of this protein, we constructed chimeras containing different N-terminal portions of NT joined to a reporter sequence, the ectodomain of a type II surface membrane protein. These chimeric proteins were found to be retained in the Golgi apparatus as assessed by cell surface biotinylation and immunofluorescence. We found that the transmembrane domain of NT is sufficient to confer Golgi retention of the fusion proteins and propose that it contains the Golgi retention signal of the parent molecule.