Significance Human coronavirus OC43 arose relatively recently, presumably from a bovine coronavirus spillover. Both viruses use 9- O -acetylated sialoglycans as receptors to which they attach via spike protein S. Another envelope protein, hemagglutinin-esterase (HE), serves as a receptor-destroying enzyme. We demonstrate that HE and S are functionally intertwined and that receptor destruction and receptor binding need to be carefully balanced for efficient (pre)attachment. During early emergence of OC43 this balance was reset, presumably as an adaptation to the human host. Such a two-protein mechanism for dynamic virion attachment is unique among coronaviruses, but reminiscent of that of influenza A viruses. Apparently, general principles fundamental to virion–sialoglycan interactions prompted convergent evolution of two zoonotically-relevant groups of pathogens.