HIV-1 envelope architecture: Which glycoprotein is the transmembrane ‘‘pedicle’’ (fusion) subunit of the HIV-1 envelope complex?

Introduction / Context:
The HIV-1 envelope complex is composed of gp120 (surface) and gp41 (transmembrane). Distinguishing their roles clarifies how entry inhibitors and fusion blockers work.

Given Data / Assumptions:

• gp41 spans the viral envelope and drives membrane fusion.
• gp120 binds CD4 and co-receptors.
• The item asks specifically for the transmembrane pedicle component.

Concept / Approach:
After gp160 cleavage, gp120 remains peripheral while gp41 anchors and undergoes conformational changes to fuse viral and cellular membranes. This makes gp41 the transmembrane ‘‘pedicle’’ subunit.

Step-by-Step Solution:
Identify which subunit is transmembrane and fusogenic → gp41.Exclude gp120 (surface binding), and the nonstandard labels listed.Select ‘‘gp 41’’.

Verification / Alternative check:
Fusion inhibitors (e.g., enfuvirtide) target gp41 interactions, reinforcing this function.

Why Other Options Are Wrong:
gp120 is not transmembrane; the other designations are incorrect or unrelated to HIV-1 envelope components.

Common Pitfalls:
Interchanging gp120 and gp41 due to their co-localization in the envelope trimer.

Final Answer:
gp 41.