Molecular basis for occlusion of the jeilongvirus receptor-binding site by the elongated C-terminus.

Paramyxoviral transmission between hosts may be, in part, attributed to the ability of the viral envelope-displayed receptor-binding protein (RBP) to bind to cell surface receptors of different host species. We sought to elucidate the architecture of the receptor-binding head region of the RBPs presented by jeilongviruses, a group of emerging and genetically unique paramyxoviruses belonging to the genus IMPORTANCE: The paramyxovirus receptor-binding protein (RBP) plays a primary role in determining cell and species tropism. Here, we study the RBPs of jeilongviruses, a group of paramyxoviruses that present a distinctive RBP that encodes an elongated C-terminal region. While the jeilongviral RBP structurally categorizes with paramyxoviral RBPs that interact with sialic acid during host-cell entry, the unusually long C-terminal domain was found to sterically occlude the associated binding site, suggesting that the molecule has developed strategies for autoinhibition of receptor interactions. These data expand our understanding of the architectural space occupied by paramyxoviral RBPs and the structural elaborations that may be incorporated into the paramyxovirus genome to modulate native functionality.