The VRG4, gene encodes an essential Golgi GDP-mannose transporter which supplies the lumenal substrate used by all of the yeast mannosyltransferases. Because of its pivotal role in regulating glycosylation and cell wall biosynthesis in yeast, we have undertaken a detailed analysis of this protein.
Several questions are of interest.
Second, how is this protein localized to the Golgi. To identify regions of the protein important for function we are trying to correlate various structural domains of Vrg4p that are important for function. Towards this end we have developed a variety of different assays for function. We found that Vrg4p exists as a homo-oligomer in the Golgi. Mutational analysis has identified several distinct domains that are important for each of these properties.