Table 2.
Average thermodynamic parameters for TAR binding by TBPs and peptides at 20 °C
| Sample | KD | Sites (n) | ΔΗ° | −TΔS° | ΔG° | ΔΔGa | Krelb | β2-β3 loop (residues 47–52) |
|---|---|---|---|---|---|---|---|---|
| nm | kca/mol | kcal/mol | kcal/mol | kcal/mol | ||||
| TBP6.3 | 45.2 ± 3.4 | 1.0 | −18.4 ± 1.7 | 8.5 ± 1.8 | −9.9 ± 0.1 | 1.2 | 8.5 | RTRRPR |
| TBP6.6 | 4.2 ± 0.3 | 1.0 | −24.8 ± 0.5 | 13.6 ± 0.6 | −11.3 ± 0.1 | −0.2 | 0.8 | RTRTPR |
| TBP6.7 | 5.3 ± 0.9 | 1.0 | −25.0 ± 2.9 | 13.9 ± 2.9 | −11.1 ± 0.1 | 0.0 | 1.0 | RQRTPR |
| TBP6.9 | 3.0 ± 0.3 | 1.0 | −22.3 ± 1.6 | 11.6 ± 1.4 | −11.5 ± 0.1 | −0.4 | 0.6 | RRRTPR |
| TBP6.25 | 71.1 ± 2.0 | 1.0 | −15.3 ± 2.0 | 5.7 ± 2.0 | −9.6 ± 0.1 | 1.5 | 13.4 | RYRTPR |
| Q48R/T50Rc | 27.8 ± 6.5 | 1.0 | −16.6 ± 2.8 | 6.4 ± 2.6 | −10.2 ± 0.2 | 0.9 | 5.2 | RRRRPR |
| Tat ARM | 135 ± 31 | 2.0 | −4.5 ± 0.6 | −4.8 ± 0.7 | −9.2 ± 0.1 | NAd | NA | —e |
| TB-CP-6.9a | 5.3 ± 0.2 | 1.0 | −7.2 ± 0.2 | 0.1 ± 0.2 | −7.1 ± 0.02 | NA | NA | RRRTPR |
a
The difference of (ΔG°mutant or ΔG°variant) − ΔG°TBP6.7.
b
Defined as the ratio of [mutant KD]/[WT KD] TBP6.7.
c
A β2-β3 loop variant generated for this study based on the TBP6.7 protein.
d
NA, not applicable.
e
The Tat ARM sequence is GISYGRKKRRQRRRAHQ.