Cross effects of leader Gs12 aptamers on SMD-Ll1 activity. Activity of SMD-Ll1 in the presence of RNA aptamers selected for binding to SMD-Ll2 (Gs12-62 and Gs12-70) at SMD:RNA molar ratios of 1:10 was calculated from fluorescence measurements. SMD activity is expressed as percent of the fluorescence counts obtained with SMD-Ll1 in the absence of RNA (black bar). The effects of control aptamers selected for binding to SMD-Ll1 are also shown: Es8-20 (inhibitory RNA), and Es8-35 (noninhibitory RNA). Data shown are averages of six experiments (n = 6) except for Es8-35 (n = 3), each in triplicate, ± SEM. Significant inhibitions relative to protein alone were determined for data in n = 6 by an ANOVA of repeated measures and the Tukey post-test (*** P < 0.001).