Tiny things can make a huge difference.
A new study by researchers from the University of North Carolina at Chapel Hill brings this startlingly to light. They have shown that a single calcium atom affects the ability of Pseudomonas aeruginosato to move and to infect cells.
Pseudomonas aeruginosa, a common bacteria that can
cause fatal infection, ‘walks’ along solid surfaces by extending and retracting type IV pili. The pili attach to a surface and pull the bacteria along like a grappling hook. This crawling behavior, called twitching motility, is essential for infection.
When lead investigator Matthew R. Redinbo and his team crystallized the protein component of pili (PilY1), they found that it contained the binding site of a calcium atom. Modifying the protein so that it could no longer bind calcium prevented the formation of pili. Altering PilY1 so that it could not release calcium prevented the pili from retracting.
“We found it pretty remarkable that the binding of a single atom to a protein that is outside the cell is sufficient to tell these motors that are inside the cell to either stop pushing or stop pulling."
A single calcium atom (shown in light blue) binding to a bacterial pili protein, drawn by Michael D.L. Johnson.