Table S1.
Summary of effects of STAT3 linker domain mutants
| Mutant | Transcription activation, % | DNA off time | Intramolecular contact |
| K551A | <10 | t1/2,<1 min | E434 |
| W546A | 25–30 | t1/2, 20 min | E434 |
| W546A+K551A | 5 | ND | E434 |
| E434A | 40 | WT | K551, W546 |
| E434A/E435A | 10 | t1/2, 3 min | K551, W546, H437, R382 |
| W562A | 40–50 | ND | P471 |
| W564A | 20–25 | ND* | S611 |
| W566A | 5 | ND | — |
| D570A | 5–8 | Stable 2.5 h | K574 |
| D570K | −2 | Stable 2.5 h | K574 |
| K573A | 15 | NA | — |
| K574A | <10 | NA | D570 |
| WT | 100 | t1/2, 40 min | — |
All mutants are in linker domain except E434A (DBD), which contacts linker domain residues.
*
ND W564A is a less stable protein than wild type; see Fig. S2.