Table 1.
Enzymatic activity of linker deletion mutants of ClpA
| ATP hydrolysis1 |
Protein degradation1 |
||||
|---|---|---|---|---|---|
| ClpA form |
Activity |
Km(ATP)/Ka (casein)2 |
α-casein |
GFP-SsrA |
LR-GFPVenus |
| Vmax/Km | Vmax/Km | Vmax/Km | |||
| Wild type | 990±25 | 0.26±0.1/0.21±0.04 | 9.1±1.5/0.2±0.3 | 10±1/1.7±0.2 | 5.0±0.3/0.95±0.1 |
| Link-Δ10 | 900±35 | 0.86±0.4/0.11±0.03 | ND | 15±2/1.7±0.3 | 5.0±0.2/0.8±0.1 |
| Link-Δ15 | 1050±40 | 1.1±0.3/0.45±0.1 | 13±1/0.35±0.02 | 17±2/1.5±0.5 | 5.1±0.4/0.7±0.2 |
| ClpA-ΔN | 1020±50 | 0.25±0.2/6.0±1 | 27±2/6.0±13 | 19±1/1.0±0.3 | NA4 |
1
Units of ATPase activity are μmol ATP hydrolyzed/min/μmol ClpA6. Units of protein degradation (Vmax) are μmol protein degraded/min/μmol ClpA6. Km or Ka values are expressed as μM protein monomer. Values shown are the averages of three replicates and the error range of the measurements. LR-GFPVenus degradation was carried out in the presence of saturating ClpS (0.4 μmol).
2
Casein concentration required for half-maximal activation of ClpA6 ATPase activity.
3
Data from DeDonatis et al (2009 J. Biol. Chem. under revision).
4
NA, not applicable. ClpA-ΔN does not bind ClpS and therefore has no ClpS-dependent activity against LR-GFPVenus.