TABLE 4.
Arrhenius analysis of ATPase activities of deletion mutants ATPase activities were measured at temperatures between 25 and 50 °C as described under “Experimental Procedures.” Except where indicated, the assay medium did not contain CCCP. From the resulting Arrhenius plots (In kcat versus 1/T), the activation energy, Ea, and changes of enthalpy, ΔH‡, entropy, ΔS‡ (expressed as TΔS‡), and Gibbs free energy of activation, ΔG‡, for the rate-limiting step of the overall reaction at 50 °C were calculated. ΔΔ values give the difference of the respective parameter between wild-type and mutant enzymes (or, for wild-type enzyme, between the activities in the absence and presence of CCCP).
| Strain/mutation | Ea | ΔH‡ | ΔΔH‡ | TΔS‡ | Δ(TΔS‡) | ΔG‡ | ΔΔG‡ | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| kJ/mol | |||||||||||||
| Wild type | 72.5 | 69.8 | 2.2 | 67.6 | |||||||||
| Wild type (+CCCP) | 72.7 | 70.0 | 0.2 | 3.4 | 1.2 | 66.6 | –1.0 | ||||||
| Δ380LQDI383 | 51.8 | 49.1 | –20.7 | –18.8 | –21.0 | 67.9 | 0.3 | ||||||
| Δ384IAIL387 | 50.9 | 48.2 | –21.6 | –15.3 | –17.5 | 63.5 | –4.1 | ||||||
| Δ388GMDE391 | 52.6 | 49.9 | –19.9 | –18.5 | –20.7 | 68.4 | 0.8 | ||||||
| Δ392LSD394 | 54.2 | 51.5 | –18.3 | –14.8 | –17.0 | 66.3 | –1.3 | ||||||
| Δ381QDIIAIL387 | 36.8 | 34.1 | –35.7 | –30.6 | –32.8 | 64.7 | –2.9 | ||||||