Open AccessAssembly of cytochrome f into the cytochrome bf complex in isolated pea chloroplasts
Author(s) -
Mould Ruth M.,
Kapazoglou Aliki,
Gray John C.
Publication year - 2001
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2001.01938.x
Subject(s) - cytochrome b6f complex , cytochrome , thylakoid , cytochrome b , cytochrome f , biochemistry , cytochrome c , cytochrome c1 , biology , chloroplast , protein subunit , cytochrome c oxidase , coenzyme q – cytochrome c reductase , mitochondrion , enzyme , gene , mitochondrial dna
Structural features of cytochrome f necessary for assembly into the cytochrome bf complex were examined in isolated pea chloroplasts following import of 35 S‐labelled chimeric precursor proteins, consisting of the presequence of the small subunit of Rubisco fused to the turnip cytochrome f precursor. Assembly was detected by nondenaturing gel electrophoresis of dodecyl maltoside‐solubilized thylakoid membranes. A cytochrome f polypeptide unable to bind haem because of mutagenesis of Cys21 and Cys24 to alanine residues was assembled into the complex and had similar stability to the wild‐type polypeptide. This indicates that covalent haem binding to cytochrome f is not necessary for assembly of the protein into the cytochrome bf complex. A truncated protein lacking the C‐terminal 33 amino acid residues, including the transmembrane span and the stroma‐exposed region, was translocated across the thylakoid membrane, had a similar stability to wild‐type cytochrome f but was not assembled into the complex. This indicates that the C‐terminal region of cytochrome f is important for assembly into the complex. A mutant cytochrome f unable to bind haem and lacking the C‐terminal region was also translocated across the thylakoid membrane but was extremely labile, indicating that, in the absence of the C‐terminal membrane anchor, haem‐less cytochrome f is recognized by a thylakoid proteolytic system.