Fig. 6.

Temperature-dependent activity of PhaCCA–RR in vivo. PhaCCA–RR complements for the endogenous CCA-adding activity in E. coli at temperatures up to 34 °C. At 37 °C, however, the enzyme is not sufficiently active, indicating that the helix-capping effect does not provide enough stability to render the enzyme active at higher temperatures. EcoCCA, E. coli CCA–adding enzyme; DxD, catalytically active wild type enzyme; AxA, inactive EcoCCA variant; PhaCCA–RR, P. halocryophilus CCA–adding enzyme with K133R and N134R replacements; wt, wild type.