Table 1.
TAP activity in microsomes and proteoliposomes
| Peptides | TAP in
microsomes
|
TAP in proteoliposomes
|
|||||
|---|---|---|---|---|---|---|---|
| Peptide binding
|
Peptide
binding
|
ATPase activity
|
|||||
| KD, nM | Bmax, cpm/ng | KD, nM | Bmax, cpm/ng | TAP recovery | Km.pep, nM | Vmax, μmol/min × mg TAP | |
| RRYQKSTEL | 154 ± 9 | 0.469 ± 0.004 | 164 ± 22 | 3.245 ± 0.219 | 49.7% | 161 ± 15 | 2.02 ± 0.13 |
| RRYNASTEL | 503 ± 54 | 0.465 ± 0.024 | 516 ± 52 | 3.184 ± 0.213 | 50.2% | 574 ± 134 | 1.93 ± 0.02 |
| EPGNTWDED | >106 | ND | >106 | ND | ND | >106 | ND |
ND, not determined.
KD and Bmax values for microsomes and proteoliposomes were determined by peptide-binding assays with radiolabeled peptides and fitted as a hyperbolic curve fit. Bmax is given per nanogram total protein. TAP recovery was calculated by comparing the total amount of binding sites before and after reconstitution. Km.pep and Vmax were determined by ATPase assays, as described in Materials and Methods.