Figure 4.
Hypothetical mechanisms for the CES behavior of cytochrome f. (A) Direct interaction between the Cter domain of cytochrome f and the petA 5′ UTR. (B) Indirect interaction which relies on a putative ternary effector, TCAi, an activator of cytochrome f translation. (Left) Inhibition of cytochrome f synthesis caused by the accumulation of unassembled cytochrome f, as observed in strains lacking SUIV, but not in strains lacking accumulation of the Cter domain of cytochrome f. (Right) Activation of cytochrome f synthesis, the petA messenger (A) or the TCAi factor (B) being made available upon assembly. The intermediate rate of synthesis observed in wild-type cells results from an equilibrium between these situations.