Concluding remarks
Apo - and holo -PlzA function differently in the vertebrate and tick phases of the enzootic cycle of B. burgdorferi(14,52,55-57). We and others have suggested that the effector functions of apo -PlzA and holo -PlzA reflect distinct activities and interaction partners (14,47,53,54,57). Here, we demonstrate that c-di-GMP modulates the RNA strand displacement and unwinding activity of PlzA, suggesting these activities may be important for the vertebrate phase of the life cycle, but not the tick phase. Conversely, PlzA has c-di-GMP-independent RNA annealing activity, and we postulate that PlzA may act as a matchmaker RNA chaperone aiding in sRNA and target RNA interactions throughout the enzootic cycle of the spirochete (Fig. 7).