Table 2.
Effect of single amino acid substitutions of human IL-1β on binding to sRI and XOMA 052
| IL-1β mutant | sRI binding (RU)* | XOMA 052 kd (sec−1)** |
| wt | 130 ± 26 | ≤1 × 10−6 |
| R4A† | 121 ± 12 | ≤1 × 10−6 |
| R4D† | 7 ± 5 | ≤1 × 10−6 |
| L6A | 118 ± 2 | ≤1 × 10−6 |
| C8Y | 114 ± 7 | ≤1 × 10−6 |
| V40A | 134 | ≤1 × 10−6 |
| V41I | 132 ± 7 | ≤1 × 10−6 |
| E50A | 131 | ≤1 × 10−6 |
| E64A‡ | 126 | ≤1 × 10−5 |
| K65A‡ | 122 | ≤1 × 10−5 |
| L67A‡ | 124 ± 10 | ≤1 × 10−5 |
| Y68A‡ | 130 ± 3 | ≤1 × 10−5 |
| K93A | 65 ± 20 | ≤1 × 10−6 |
| M95A | 110 ± 6 | ≤1 × 10−6 |
| E96A | 135 ± 1 | 3 × 10−3 |
| K97A | 132 ± 1 | 2 × 10−3 |
| Q116E | 145 ± 2 | 2 × 10−3 |
| F150S | 113 ± 13 | ≤1 × 10−6 |
Mean and range of multiple measurements for those mutants measured more than one time.
Dissociation rates ≤1 × 10−5 approach the limit of measurement in this experiment, which followed dissociation for only 10 min. The curves fit as 10−5 sec−1 could be distinguished qualitatively from those fit at 10−6 sec−1, but the difference cannot be quantitatively determined from these measurements.
This residue is located in the binding interface with sRI.
These residues belong to the same loop. The slight increase in off-rates most likely results from a destabilization of the IL-1β structure because a similar decrease was observed with control anti-IL-1β antibodies with non-overlapping epitopes to XOMA 052 (data not shown).