Weakness as a strength

Jun Qin (Lerner Research Institute, Cleveland, OH) is the defender of the weak, or at least of weak protein–protein interactions. His work with Julia Vaynberg, Tomohiko Fukuda, Cary Wu (University of Pittsburgh, Pittsburgh, PA), and colleagues shows that an extremely weak affinity between two focal adhesion proteins is needed for cell migration.

The focal adhesion proteins are the adaptors PINCH-1 and Nck-2, whose weak interaction (K_D ≈ 3 mM) was noted previously in yeast two-hybrid assays but not with less sensitive techniques. Using NMR, which unlike crystallography provides structural information even for very weak interactions, the group has now determined the structure of the tiny interface between the adaptors. To prove its biological relevance, they then used genetic rescue experiments to show that the disruption of the PINCH-1/Nck-2 interface in vivo impairs cell...