Recognition of essential purines by the U1A protein

BMC Biochemistry

Table 2 Stability of complexes of wild type U1A protein with SL2 RNA sequences containing G4 modifications.

	WT	G4dG	G4c7dG	G4I	G42AP	G4DAP	G4A
K_D (M)^a	3 ± 2 × 10^-10	1.1 ± 0.4 × 10^-10	3.1 ± 0.1 × 10^-8	3 ± 1 × 10^-9	4 ± 1 × 10^-6	2 ± 1 × 10^-6	1.1 ± 0.2 × 10^-5
ΔG (kcal/mol)^b	-13.2 ± 0.4	-13.6 ± 0.2	-10.3 ± 0.01	-11.7 ± 0.2	-7.4 ± 0.1^e	-7.8 ± 0.3	-6.8 ± 0.1^e
ΔΔG^c		-0.4	3.3^d	1.5	5.8	5.4	6.4

^aK_D values are the average of at least three independent experiments. Standard deviations determined from the independent measurements are reported. ^bΔG is the free energy of association of the complex. ^cΔΔG is the difference between the binding free energies of the wild type U1A protein for SL2 RNA containing the indicated base substitution and wild type SL2 RNA. ^dΔΔG is the difference between the binding free energies of the wild type U1A protein for SL2 RNA containing the indicated base substitution and SL2 RNA containing G4dG. ^e These binding curves did not reach saturation. Thus, the binding constants given were estimated by assuming saturation would be reached at 70–100% bound as discussed in the experimental section.

ISSN: 1471-2091