3D illustration of spherical-shaped, measles virus particle, that is studded with glycoprotein tubercles. These tubercular studs colorized maroon, are known as H-proteins (hemagglutinin), while those colorized gray, represented what are referred to as F-proteins (fusion). The F-protein is responsible for fusion of the virus and host cell membranes, viral penetration, and hemolysis. The H-protein is responsible for the binding of virions to cells. Both types of proteinaceous studs are embedded in the particle envelope's lipid bilayer.