The information for recognition and interaction with host cell lies in the protein component. The site on the host cell to which the virus binds is known as the receptor, and is specific for different viruses. The site on the virus, which binds to the host cell, is the viral ligand. Quite often the proteins surrounding the virus have enzymatic activity essential for virus replication. These include enzymes necessary for viral nucleic acid replication, and the reverse transcriptase, Other proteins may be involved in receptor binding and enzymatic activity involved in this binding e.g. neuraminidase in influenza virus.
Viruses come in two main shapes, spherical, or rod like.
Although they may appear pleomorphic in electron microscopic analysis, this is due to the lipid bilayer membrane envelope found around many viruses. Only way of visualizing viruses is by electron microscopy or computer modeling following X-ray diffraction. Will be discussed briefly in this lecture and will be the subject of a talk later on by Dr. Ybe. 2-3Ao DNA double helix is 20 angstroms Some terminology. Free virus particle.