The binding of Class II sRNA MgrR to two different sites on matchmaker protein Hfq enables efficient competition for Hfq and annealing to regulated mRNAs

Comparison of sRNAs in competition for binding to Hfq. The dissociation of ³²P-MgrR sRNA from Hfq was initiated by adding unlabeled sRNA competitors at 5 nM concentration. The fitting of the data using segmental linear regression provided and values of, respectively, 250 × 10⁻⁴ sec⁻¹ and 4 × 10⁻⁴ sec⁻¹ for ChiX, 7.2 × 10⁻⁴ sec⁻¹ and 0.64 × 10⁻⁴ sec⁻¹ for CyaR, 170 × 10⁻⁴ sec⁻¹ and 14 × 10⁻⁴ sec⁻¹ for DsrA, 5 × 10⁻⁴ sec⁻¹ and 2.9 × 10⁻⁴ sec⁻¹ for McaS, 110 × 10⁻⁴ sec⁻¹ and 4.7 × 10⁻⁴ sec⁻¹ for MgrR, 37 × 10⁻⁴ sec⁻¹ and 0.29 × 10⁻⁴ sec⁻¹ for RyhB. Average k_off values are presented in Table 2.