Signalling protein binds by mutually induced fit

Most biological processes in the cell involve one protein binding to another protein to initiate a reaction. The ability of a protein to bind to another requires a high degree of specificity between the two binding structures, and the molecular structure is dictated by the sequence of amino acids that make up the proteins involved.

To understand how some proteins are able to bind many different proteins, a team of researchers, including Dirar Homouz from Khalifa University in Abu Dhabi, looked at the signalling protein calmodulin (CaM), a well-known protein that can bind to hundreds of other cellular proteins. They measured the association rates of CaM with two such binding targets, CaMKI and CaMKII peptides, and compared it to computational models for association rate calculation.

They found that the proteins interaction happens in two stages. In the first stage, CaM has a protruding structure and the target protein is bound by a certain part of the protein called the C domain. CaM then adopts a spheroid conformation and the target repositions closer to the binding pocket.

These results support the mutually-induced fit model, in which both proteins change their conformation upon binding, providing a potential explanation for the dynamics of protein binding.

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