Table 1.

Binding affinities, stoichiometries and thermodynamic parameters for the interaction between LST-1 peptides and FBF-2 measured by ITC

LST-1 variant	Sequence1	K d (μM)2	N (# of sites)3	ΔH (kJ/mol)	ΔG (kJ/mol)	-TΔS (kJ/mol)
LST-119–50 A	QHEAPKQLLQLRSEIK	2.13	0.88	-57.3	-31.9	25.4
		2.02	0.85	-57.1	-32.0	25.1
LST-167–98 B	GLRSQKLHLTYIEKNK	0.046	0.87	-73.4	-41.2	32.2
		0.045	0.88	-71.3	-41.3	30.0
LST-119–50 A	QHEAPKQLLQLRSEIK	2.41	1.0	-50.6	-31.6	19.0
		2.29	1.0	-50.4	-31.7	18.7
LST-167–98 B	GLRSQKLHLTYIEKNK	0.052	1.0	-64.2	-40.9	23.3
		0.051	1.0	-62.5	-41.0	21.5
LST-1 B mutN	GHEAPKLHLTYIEKNK	0.21	1.0	-56.3	-37.6	18.7
		0.24	1.0	-53.7	-37.2	16.5
LST-1 B mutC	GLRSQKLHLTLRSENK	1.51	1.0	-42.7	-32.7	10.0
		1.45	1.0	-43.5	-32.8	10.7
LST-1 B Y85L	GLRSQKLHLTLIEKNK	0.74	1.0	-50.3	-34.4	15.8
		0.85	1.0	-50.3	-34.1	16.2

¹The relevant portions of the amino acid sequences of LST-1 A (residues Q27-K42) and LST-1 B (residues G75-K90) are shown. Complete peptide sequences are in Figure 1. The lysine and leucine residues in the KxxL motifs are in boldface. The substitutions in the mutant peptides are blue.

²Two technical replicates were performed for each analysis, and the values for each replicate are shown.

³For the analysis of LST-1 A and LST-1 B, we determined the LST-1 titrant concentrations by A₂₈₀. For the analysis of LST-1 B mutants, the number of sites, N, was set at 1 during curve fitting while the LST-1 B concentration was fit, because we could not accurately determine the titrant concentration for LST-1 B mutC and Y85L due to a lack of aromatic residues. For consistency, we also show the binding affinities and thermodynamic parameters for LST-1_19–50 A and LST-1_67–98 B when N was set at 1. The concentrations of titrants were fit to values similar to those that could be determined by A₂₈₀. The LST-1 A_19-50 concentration was fit to 0.24 mM vs 0.28 mM by A₂₈₀, the LST-1 B_67-98 concentration was fit to 0.14 mM vs 0.12 mM by A₂₈₀, and the LST-1B mutN concentration was fit to 0.16 mM v 0.12 mM by A₂₈₀.