Question:medium
Binding of gp120 causes:
Binding of gp120 causes:
Show Hint
gp120 binds CD4 first, then exposes the site that engages CCR5 or CXCR4.
Updated On: Jun 24, 2026
- Infection of target cell
- Facilitation of co-receptor
- Fusing of virus and target cell
- None
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: HIV uses an ordered handshake with the host cell. Knowing which envelope protein does what is the key to this item.
Step 2: gp120 is the docking protein. Its first job is to latch onto CD4. That attachment reshapes gp120 so that it can now reach the chemokine co-receptor, either CCR5 or CXCR4. In other words, gp120 binding sets up and facilitates co-receptor engagement.
Step 3: What gp120 does not do directly is merge the membranes; that step belongs to gp41, whose fusion peptide drives the envelope into the cell membrane. And calling the result simple infection skips the intermediate co-receptor step that the question is probing.
Step 4: So the precise consequence of gp120 attaching is to enable the co-receptor to come into play.
\[\boxed{\text{Facilitation of co-receptor}}\]
Step 2: gp120 is the docking protein. Its first job is to latch onto CD4. That attachment reshapes gp120 so that it can now reach the chemokine co-receptor, either CCR5 or CXCR4. In other words, gp120 binding sets up and facilitates co-receptor engagement.
Step 3: What gp120 does not do directly is merge the membranes; that step belongs to gp41, whose fusion peptide drives the envelope into the cell membrane. And calling the result simple infection skips the intermediate co-receptor step that the question is probing.
Step 4: So the precise consequence of gp120 attaching is to enable the co-receptor to come into play.
\[\boxed{\text{Facilitation of co-receptor}}\]
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