Table 2.

Characteristics of N-terminal residues in relation to mutant SC(1–246) affinity and ProT^QQQ activation potency

N-terminal mutants	Residue 1 characteristics	Residue 2 characteristics	Affinity range (KD)	Activation potency normalized (Vlim)	Free energy (ΔG)
			nm
I1V2 WT	Nonpolar	Nonpolar	0.7 ± 0.2	1.0	−12.48
V1V2, I1A2, and L1V2	Similar nonpolar	Similar nonpolar	∼0.9–1.3	∼1.0–1.80	− 12.33 to − 12.11
I1T2, I1W2, I1L2, and V1G2	Similar nonpolar	Polar, nonpolar, indole	∼5–100	∼0.9–1.60	− 11.29 to − 9.55
T1V2, T1P2, and T1A2	Polar	Nonpolar, pyrrolidine	∼11–100	∼0.4–1.70	− 10.88 to − 9.55
L1T2, L1Q2, L1K2, and L1P2	Similar nonpolar	Nonpolar, pyrrolidine, charged	∼19–220	∼0.3–1.6	− 10.54 to − 9.08
W1A2 and W1E2	Indole	Nonpolar, charged	∼117–191	NDa	− 9.45 to − 9.17
M1L2, M1W2, M1K2, and M1E2	Bulky nonpolar	Nonpolar, indole, charged	∼127–514	∼0.06–1.1	− 9.40 to − 8.58
G1H2, G1A2, G1P2, G1D2, G1G2, A1W2, A1K2, A1S2, and A1T2	Small nonpolar	Small nonpolar, polar, charged, aromatic	∼153–503	∼0.02–1.0	− 9.29 to − 8.62
Q1K2, T1D2, S1K2, Q1L2, and N1D2	Polar	Charged, nonpolar	∼169–493	∼0.02–0.24	− 9.24 to − 8.58
R1R2, K1A2, E1T2, R1Q2, and E1S2	Charged	Charged, nonpolar, polar	∼379–650	∼0.004–0.1	− 8.76 to − 8.44

^a ND, not determined.