Model for the biogenesis of the S. coelicolor Rieske protein. (1) SRP binds to the first hydrophobic segment of Sco2149 emerging from the ribosome, and guides the complex to the Sec machinery. (2) The first two TMs of Sco2149 are inserted into the membrane cotranslationally. (3) The iron-sulfur cluster is inserted into Sco2149, leading to folding of the globular domain. (4) The Tat system translocates the Fe-S domain. (5) Fully assembled Sco2149 is released into the membrane, where it can interact with its partner subunits to form the cytochrome bc₁ complex.