Homomeric interactions between transmembrane proteins of Moloney murine leukemia virus

We have studied homomeric interactions between transmembrane proteins (TM) of the Moloney murine leukemia virus envelope using the Saccharomyces cerevisiae two-hybrid system. TM interacts strongly with itself but not with various control proteins. Deletional and mutational analyses indicated that the putative leucine zipper motif in the extracellular domain of TM is essential and sufficient to mediate the binding. The first three repeats of the leucine zipper-like motif are the most important in mediating the interaction. The TM-TM interaction detected in this system may play a role in several stages of viral replication. Envelope proteins of retroviruses, including those of Molo-ney murine leukemia virus (Mo-MuLV), are synthesized in infected cells as a glycoprotein precursor (19, 41; for a review, see reference 16). These glycoproteins form oligomers in the lumen of the endoplasmic reticulum and are subsequently cleaved in the Golgi apparatus by host proteases into two subunits: the extracellular surface protein (SU) and the trans-membrane protein (TM) which spans the membrane (12, 27). SU and TM remain associated with each other and are an