Daniel Luque, The University of New South Wales

Dunia Asensio-Cob1 , Carlos P. Mata2, Josué Gómez-Blanco3, Javier Vargas4, Javier M. Rodríguez2, Daniel Luque5,6 1 Department of Molecular Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto ON, M5G0A4, Canada. 2 Departamento de Estructura de Macromoléculas, Centro Nacional de Biotecnología, CSIC, Cantoblanco, 28049 Madrid, Spain. 3 Artis Analytica Scientia S.L., Madrid 28021, Spain. 4 Departamento de Óptica, Universidad Complutense de Madrid, Madrid 28040, Spain 5Electron Microscope Unit, Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW 2052, Australia. 6 School of Biomedical Sciences, University of New South Wales, Sydney, NSW 2052, Australia.

Structural Biology

The infectivity of rotavirus (RV), the leading cause of childhood diarrhea, hinges on the activation of viral particles through the proteolysis of the spike protein by trypsin-like proteases in the host intestinal lumen. Despite comprehensive structural characterization of the virus particle, the structural rationale behind the necessity of trypsin digestion of the VP4 protein for infectivity remains poorly understood. In this study, using cryo-electron microscopy (cryo-EM) and advanced image processing techniques, we compared uncleaved and cleaved RV virions and found that the conformation of the non-proteolyzed spike is constrained by the position of loops that surround its structure, linking the lectin domains of the spike head to its body. The proteolysis of these loops removes this structural constraint, thereby enabling the spike to undergo the necessary conformational changes required for cell membrane penetration. Thus, these loops function as regulatory elements to ensure that the spike protein is activated precisely when and where it is needed to facilitate a successful infection.