Figure 7.

The outcome for genetic regulation is determined following the synthesis of the aptamer domain. Here, SAM binding shifts the equilibrium of pseudoknot associated contacts toward engagement (top pathway). The contacts provide aptamer stability leading to the continued exclusion of the AT strand following its elongation. In the absence of SAM binding the AT strand is free to compete with an unstablized open conformation of the aptamer leading to the formation of the AT helix (lower pathway).