Oligomerization of a membrane protein correlates with its retention in the Golgi complex

The experiments presented here support protein oligomerization as a mechanism for retaining the chimeric protein Gml in the Golgi complex. An unusual feature of the Gml oligomer (its resistance to solubflization by SDS) allowed us to easily assay oligomer formation. The specificity of oligomerization was mediated by the ml transmembrane domain, since mutant Gml proteins that were retained in the Golgi formed oligomers, while mutant proteins that were released to the plasma membrane did not. This specificity was preserved in another construct, otmlG, in which the lumenal domain of VSV G was replaced with the o~ subunit of hCG. Furthermore, e~mlG was able to form hetero-oligomers with Gml and other Golgi-resident Gml mutants, but not with mutants that move to the plasma membrane. This suggested that the lumenal domain of VSV G was not required for oligomerization.