TABLE 2.
Inosine uptake by single cysteine mutants of TM4 and change in inosine uptake following MTSEA or MTSES treatment of Δldnt1/Δldnt2 cells
| Residuea | Inosine uptakeb | Uptake inhibition by |
|
|---|---|---|---|
| MTSESc | MTSEAc | ||
| ΔCys | ● | N | N |
| H138C (out) | ●● | N | N |
| G139C | ● | N | N |
| A140C | ●● | N | N |
| I141C | ● | N | N |
| A142C | ●● | N | N |
| V143C | ●
|
N | N |
| I144C | |
N | N |
| M145C | ● | N | N |
| V146C | ● | N | N |
| V147C | |
N | N |
| A148C | |
N | N |
| C149C | |
N | N |
| V150C | |
N | N |
| G151C | |
N | N |
| G152C (n = 2) | ● | −35% | −93% |
| F153C | ● | N | N |
| S154C (n = 2) | ○ | N | −77% |
| K155C (n = 3) | ○ | N | +360% |
| A156C (n = 2) | ○ | −30% | −95% |
| L157C | |
N | N |
| C158C | |
N | N |
| D159C (n = 2) | |
−65% | −80% |
| S160C | ●●● | N | N |
| C161C | ●●● | N | N |
| T162C | ● | N | N |
| N163C (n = 3) | |
N | N |
| A164C | ●●● | N | N |
| L165C | ● | N | N |
| V166C | |
N | N |
| G167C (n = 2) | |
N | −65% |
| P168C | ● | N | N |
| F169C | |
N | N |
| P170C (n = 2) | |
N | −80% |
| T171C | ● | N | N |
| K172C (in) | ● | N | N |
a Position of single cysteine residue within the cfnt2-ΔCys background. n indicates the number of times a ligand protection experiment was performed for the indicated construct. “Out” indicates the extracellular end of the helix, and “in” indicates the intracellular end.
b Each and ● indicates 5 and 10 pmol of [3H]inosine/min/107 cells transported, respectively (e.g. ● indicates 15 pmol of [3H]inosine/min/107 cells). ○ indicates transport of approximately 1 pmol of [3H]inosine/min/107 cells.
c N indicates inhibition of [3H]inosine uptake similar to that measured for cfnt2-ΔCys cells. Italic type indicates that there was no protection offered by the presence of 1 mm inosine during treatment, and boldface type indicates that there was ∼50% protection.