Figure 9.

CbrR binds both GTP and c-di-GMP. To ascertain the ability of CbrR to bind nucleotides, purified CbrR was mixed with radio-labeled GTP and c-di-GMP and spotted on a nitrocellulose membrane. Imaging of proteins that bind radio-labeled nucleotide show a dark, intense spot in the middle of the membrane, while nucleotide that does not bind protein diffuses across the membrane to appear as a dark circle around the membrane where the solution was spotted. DRaCALA assays show that CbrR binds GTP (A) and c-di-GMP (B) in a similar manner. Competition binding shows a slightly higher affinity of CbrR binding GTP over c-di-GMP (C,D).