Engineering an interfacial zinc site to increase hormone-receptor affinity.
BACKGROUND
Human growth hormone (hGH) binds to both the hGH and human prolactin (hPRL) receptors. Binding to the hPRL receptor, however, is approximately 50-fold tighter and requires a single Zn2+ cation, unlike binding of hGH to the hGH receptor. Previous mutational studies have identified putative ligands from hGH and the hPRL receptor responsible for coordinating the interfacial Zn2+.


RESULTS
One of these ligands was introduced at a structurally analogous site in the extracellular domain of the hGH receptor by mutating Asn218 to His, and the resulting mutant protein showed a 20-fold increase in hGH binding in the presence of ZnCl2. Alanine-scanning mutagenesis showed that the binding site on hGH for the Asn218-->His hGH receptor in the presence of Zn2+ resembled that for the hPRL receptor.


CONCLUSIONS
It is possible to introduce the metal-binding site from the hPRL receptor into the homologous hGH receptor. More generally, these studies indicate that affinity between two proteins may be enhanced by design of an interfacial metal-binding site.
Matthews
D J
DJ
Department of Protein Engineering, Genentech, Inc., South San Francisco, CA 94080, USA.
Wells
J A
JA
D001665:Binding Sites; D005818:Genetic Engineering; D006801:Humans; D009154:Mutation; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
D011956:Receptors, Cell Surface; D015032:Zinc