Two Proteins Make Reversible Molecular Switch

Nanotechnology researchers have designed a molecular switch by combining two unrelated proteins in a way that causes the response to a specific stimulus by one of the proteins to control the activity of the other.

Investigators at Johns Hopkins University (Baltimore, MD, USA) working with Escherichia coli circularly permuted the gene encoding TEM1 â-lactamase and subsequently randomly inserted it into the gene encoding E coli maltose binding protein. This technique led to the isolation of nearly 27,000 hybrid variations of the two fused proteins. One isolate (RG13) was identified in which its â-lactam hydrolysis activity was inhibited by the absence of maltose but increased 25-fold in its presence. Upon removal of maltose, RG13's catalytic activity returned to the level seen prior to addition of maltose, illustrating that the switching was reversible. These findings were published in the November 2004 issue of Chemistry & Biology.

Senior author Dr. Marc Ostermeier, assistant professor of chemical and biomolecular engineering at Johns Hopkins University, said, "With the new technique, we have produced a molecular switch that is over 10 times more effective. When we introduce this switch into bacteria, it transforms them into a working sensor. We have proven that we can make effective molecular switches. Now, we want to use this idea to create more interesting and more useful devices.”



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