- Tropogen
The
protein on the outer surface of a virus that combines with thecellular receptor for thevirus . The interaction between the viral tropogen and the cellular receptor is quite specific. This interaction may play a role in determining tissue tropism and host range.An example of a tropogen is gp120, an
envelope glycoprotein ofHIV . gp120 combines in a specific fashion to its cellular receptorCD4 , a protein found on various cells in the human immune system includingT-helper cells , andmacrophage .
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