David Auble
Here is an example of how an extended, flexible stretch of polypeptide interacts with a globular domain of another protein. The acidic C-terminal domain of the human TFIIE α subunit binds to the pleckstrin homology domain (PH-D) of the human TFIIH p62 subunit. (PH-Ds are found in a multitude of signaling molecules and are famously involved in phosphoinositide binding as well.) In this image, which was derived from 2rnr, the acidic C-terminal domain of TFIIE α is shown in yellow and the PH-D domain of p62 is shown in blue. A feature of this interaction is that although TFIIE α polypeptide is extended, the interactions with p62 are much more extensive than one might expect. About 2300 square angstroms of surface area are occluded in the complex. Thus, interactions mediated by contiguous, unstructured stretches of amino acids need not be short and low affinity.
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