Figure 1.

The populations are dynamic and are affected by various factors, including binding. Ligand binding could allosterically affect a second binding site. Because different ligands can allosterically lead to different (second site) conformations and these sites can then select other partners, the effects can propagate downstream through altered signal transduction pathways. (a) A high energy barrier may separate the open and closed conformations, as observed for the Eph receptor[2] Sixteen Eph receptor conformations co-exist in two crystals, with eight in each asymmetric unit. Eleven of these can be classified as closed conformations, and five as open. (b) Different conformations of the protein can bind multiple ligands via conformational selection. Protein conformational change at one site (BS1) is cooperatively coupled with a change in another site (BS2), in the same or another domain. The conformational selection in BS1 can be coupled with the conformational changes in the BS2. In turn, these conformational changes in BS2 can influence signal transduction pathways through subsequent binding events. The open and closed Eph conformations are taken from Figure 2b,c in [2], with permission from BMC Biophysics

Nussinov and Ma BMC Biology 2012 10:2   doi:10.1186/1741-7007-10-2
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