Two molecular locks make a cellular pump move in only one direction.

Cells use tiny protein pumps called ABC transporters to move molecules across their membranes. Scientists did not know how fuel called ATP pushes these pumps to move in only one direction. Researchers studied this process and found two chemical bridges, called ionic locks, inside the protein. Here is how it works. A fuel unit called Mg 2+ -ATP acts like a key that breaks the inward-facing lock. This break powers the pump forward. After the fuel is used, the pump drops a piece called gamma-phosphate. This loss breaks the outward-facing lock, triggering the backward step. Because different parts of the pump become slow bottlenecks during the forward and backward steps, the pump moves in a set direction across this family of proteins.

Why it matters

ABC transporters are a large family of proteins that move molecules across cell membranes. This work explains how their one-way motion comes from two molecular locks that open in sequence. Because the same locks appear across the whole superfamily, the finding points to a shared design principle that could guide efforts to control these pumps.

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