Interaction in vitro; protein produced as a recombinant fusion protein in bacterial system;

The interaction detailed in this paper is between two isoforms of Mef2 that contain point mutations (Mef2 30-5 and Mef2 44-5) that affect the gene regulation activity of the protein homo-dimer. To determine if a physical interaction between Mef2 30-5 and Mef2 44-5 is possible, Lovato et al. carried out electrophoretic mobility shift assays, using either full length Mef2 protein or a truncated version, or a mixture of both proteins that had been synthesized in the same in vitro reaction. When mixed with the Mef2 binding site from Act57B, the individual full length and truncated isoforms generated shifted bands that were consistent with their ability to interact with DNA, and consistent with their respective sizes. The truncated isoform bound to DNA had a greater mobility than the full length Mef2-DNA complex. When the mixture of full length and truncated Mef2 was incubated with the DNA probe, a band of intermediate mobility was also observed. This band must represent an heterodimer of full lengthand truncated protein interacting with DNA.