Conversion of a maltose receptor into a zinc biosensor by computational design

We have demonstrated that it is possible to radically change the specificit y of maltose binding protein by converting it into a zinc sensor using a ra tional design approach. In this new molecular sensor, zinc binding is trans duced into a readily detected fluorescence signal by use of an engineered c onformational coupling mechanism linking ligand binding to reporter group r esponse. An iterative progressive design strategy led to the construction o f variants with increased zinc affinity by combining binding sites, optimiz ing the primary coordination sphere, and exploiting conformational equilibr ia. Intermediates in the design series show that the adaptive process invol ves both introduction and optimization of new functions and removal of adve rse vestigial interactions. The latter demonstrates the importance of the r ational design approach in uncovering cryptic phenomena in protein function . which cannot be revealed by the study of naturally evolved systems.