Table 1.
Effect of nonconservative or alanine mutations of CD2 residues on CD48 binding
| Residue | Nonconservative mutation
|
Alanine mutation
|
||
|---|---|---|---|---|
| Change | CD48 binding* | Kd† | ΔKd | |
| H12 | D | ++ | nd‡ | nd |
| N17 | D | ++ | nd | nd |
| D26 | K | ++ | 0.8 | nd |
| D28 | K | — | >20 | >20 |
| E29 | R | — | >20 | >20 |
| R31 | Y | — | >20 | >20 |
| E33 | R | — | >20 | 1.5 |
| R34 | D | ++ | 0.4 | 0.9 |
| S36 | E | ++ | 1.2 | nd |
| T37 | K | ++ | 0.5 | nd |
| L38 | Y | — | >20 | >20 |
| E41 | R | — | nd | 1.1 |
| K43 | E | — | nd | 2.0 |
| K45 | E | ++ | 0.5 | nd |
| M46 | Y | ++ | 0.8 | nd |
| K47 | D | ++ | 1.1 | nd |
| F49 | R | — | >20 | >20 |
| K51 | E | ++ | 2.9 | 1.3 |
| S52 | E | ++ | 2.2 | nd |
| E56 | R | ++ | 1.2 | 1.2 |
| R70 | E | ++ | nd | nd |
| T79 | E | ++ | 2.3 | nd |
| Y81 | S | — | >20 | >20 |
| T83 | D | ++ | 2.1 | nd |
| T86 | D | + | >20 | 0.7 |
| R87 | E | — | >20 | 0.2 |
| N90 | K | ++ | 2.4 | nd |
| D94 | K | ++ | 1.9 | nd |
*
Binding was measured as in Fig. 2 and quantified as follows: ++, binding >60% of wild-type level; +, binding detectable but <5% of wild-type level; — no detectable binding.
†
Dissociation constant measured by equilibrium binding as in Fig. 3; the figures represent the fold increase in the Kd of sCD48 binding to the mutant compared with wild-type CD2 measured in the same experiment. Where no or little binding was detected at 1.5 mM sCD48 the Kd was assumed to be >1.5 mM. The Kd for sCD48 binding wild-type CD2 was 80 ± 6 (mean ± SD, n = 4).
‡
nd, not done.