TABLE 3.

Kinetics of fH binding to fHbp subvariants based on surface plasmon resonance analysis

fHbp variantaka (M−1 s−1)kd (s−1)bRelative kdcKD (nM)
1.1I1.43 × 1050.65 × 10−21.045
1.43.38 × 1051.86 × 10−22.955
1.102.85 × 1055.09 × 10−27.8178
1.14II2.23 × 1057.16 × 10−211.0350
1.550.76 × 1050.78 × 10−21.2102
1-2,3.x0.87 × 1051.65 × 10−22.5190
2.160.96 × 1050.42 × 10−20.744
2.190.54 × 1050.21 × 10−20.340
2.220.45 × 1050.22 × 10−20.348
2.25III0.60 × 1050.04 × 10−20.17
3.281.66 × 1050.26 × 10−20.416
3.450.59 × 1050.09 × 10−20.116
  • a See Table 1 for fHbp subvariant details. Replicate measurements for representative subvariants (shown with superscript roman numerals) were as follows: I, medium-affinity fH binder fHbp 1.1, ka of (1.43 ± 0.21) × 105, kd of (0.65 ± 0.13) × 10−2, and KD of 45 ± 5; II, low-affinity fH binder fHbp 1.14, ka of (2.23 ± 0.28) × 105, kd of (7.16 ± 1.39) × 10−2, and KD of 350 ± 115; III, high-affinity fH binder fHbp 2.25, ka of (0.60 ± 0.08) × 105, kd of (0.04 ± 0.01) × 10−2, and KD of 7 ± 0.5. P values, calculated using Student's t test, for comparisons of the other two representative subvariants to fHbp 1.1 were as follows: for fHbp 1.14, P = 0.08 for ka, P = 0.01 for kd, and P = 0.06 for KD; for fHbp 2.25, P = 0.06 for ka, P = 0.03 for kd, and P = 0.01 for KD.

  • b A lower kd value corresponds to higher-affinity binding.

  • c The kd of fH binding for each subvariant relative to subvariant 1.1.