Cryo-EM reconstruction of Sindbis Virus. Cryo-EM reconstruction of Sindbis Virus at neutral pH (pH 7.0) and at low pH (pH 5.3) illustrating the conformational change that occurs at this threshold pH. The green arrow highlights the protrusion that appears at the 5-fold vertex at low pH.
Reprinted by permission from Elsevier from: Paredes, A. M., Ferreira, D., Horton, M., Saad, A., Tsuruta, H., Johnston, R., Klimstra, W., Ryman, K., Hernandez, R., Chiu, W., and Brown, D. T. (2004). Conformational changes in Sindbis virions resulting from exposure to low pH and interactions with cells suggest that cell penetration may occur at the cell surface in the absence of membrane fusion. Virology 324 (2), 373-86.