3GJN: Following Evolutionary Paths To High Affinity And Selectivity Protein- Protein Interactions Using Colicin7 And Immunity Proteins

How do intricate multi-residue features such as protein-protein interfaces evolve? To address this question, we evolved a new colicin-immunity binding interaction. We started with Im9, which inhibits its cognate DNase ColE9 at 10(-14) M affinity, and evolved it toward ColE7, which it inhibits promiscuously (Kd > 10(-8) M). Iterative rounds of random mutagenesis and selection toward higher affinity for ColE7, and selectivity (against ColE9 inhibition), led to an approximately 10(5)-fold increase in affinity and a 10(8)-fold increase in selectivity. Analysis of intermediates along the evolved variants revealed that changes in the binding configuration of the Im protein uncovered a latent set of interactions, thus providing the key to the rapid divergence of new Im7 variants. Overall, protein-protein interfaces seem to share the evolvability features of enzymes, that is, the exploitation of promiscuous interactions and alternative binding configurations via 'generalist' intermediates, and the key role of compensatory stabilizing mutations in facilitating the divergence of new functions.
PDB ID: 3GJNDownload
MMDB ID: 76715
PDB Deposition Date: 2009/3/9
Updated in MMDB: 2009/10
Experimental Method:
x-ray diffraction
Resolution: 2.48  Å
Source Organism:
Similar Structures:
Biological Unit for 3GJN: monomeric; determined by author and by software (PISA)
Molecular Components in 3GJN
Label Count Molecule
Protein (1 molecule)
Colicin-e9 Immunity Protein(Gene symbol: ceiI)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB