Figure 9. Organization of retroviral Env glycoproteins.

Figure 9

Organization of retroviral Env glycoproteins. Targeting of Env proteins to the ER is mediated by a small hydrophobic signal peptide (small black rectangle) contained within a larger leader sequence at the amino terminus of the nascent protein. The leader is removed cotranslationally during translocation across the ER membrane. Release of the polyprotein into the lumen of the ER is prevented by the large hydrophobic membrane anchor located near the carboxyl terminus of Env (large black rectangle). The SU and TM sequences are separated by the action of a host-encoded protease after transport to the Golgi apparatus, and this cleavage exposes the hydrophobic fusion peptide near the amino terminus of TM (colored rectangle). In the cases of MLV and M-PMV, the viral protease cleaves within the cytoplasmic domain of TM after Env is incorporated into the virion. The length in amino acids of each processed segment of the Env protein is shown below the line.

From: Synthesis and Organization of Env Glycoproteins

Cover of Retroviruses
Coffin JM, Hughes SH, Varmus HE, editors.
Cold Spring Harbor (NY): Cold Spring Harbor Laboratory Press; 1997.
Copyright © 1997, Cold Spring Harbor Laboratory Press.

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