How does ATP change the shape of a transport protein?

[obiwankenobi]

Hi,

Could someone explain to me how exactly ATP changes the shape of a transport protein? If ATP, when hydrolyzed, releases free energy, how does this energy change the conformation of the structure of the protein? Additionally, why must a phosphate group attach itself to it?

Thanks!

 

[Ygggdrasil]

Most enzymes bind their substrates in pockets in the interior of the protein. The different states associated with ATP hydrolysis (ATP --> ADP + Pi --> ADP) will have very different shapes that can cause changes to the shape of the pocket surrounding the nucleotide. For example, after ATP hydrolysis, you have the beta and gamma phosphate groups moving apart, which can induce changes to the surrounding protein, as can the reduction in size of the pocket that occurs when the phoshpate leaves. These changes to the shape of the nucleotide binding pocket can propagate throughout the protein, causing larger conformational changes throughout the protein. The nucleotide binding pockets of ATPases often occur at the interface between different subdomains of the protein, so changes to the shape of the nucleotide binding pocket will greatly change the quaternary structure of the protein.

Most of the active transporters that directly use the energy of ATP (as ATPases) don't attach the phosphate to themselves. Other proteins can attach phosphates to these or other proteins in the cell, and the phosphate can alter the structure of the protein or its interaction with other proteins.