UL49.5 and gM interaction involves both covalent and non-covalent forces . Both proteins are linked by a disulfide bond formed between the cysteine residue C46 present in the luminal domain of UL49.5 (numbering in a protein with a signal sequence) and the cysteine residue C59 present in the largest loop of gM. Strikingly, disulfide bonding is not required for their co-transport to the TGN, whereas the interaction of UL49.5 with gM appears to be necessary .