title: Genes and transcripts for the polypeptides of the cytochrome b6/f complex from spinach thylakoid membranes.
abstract: Cytochrome b6/f complex was prepared from washed thylakoid membranes by a procedure involving detergent treatment and centrifugation in sucrose gradients. The complex is composed of at least four polypeptide species, cytochrome f which occurs in two variant forms (mol. wt. 34/33 kd), cytochrome b6 (23 kd), the high-potential Rieske iron-sulfur protein (19 kd) and a fourth subunit (17 kd) of unknown function. Transcripts for the cytochromes f, b6 and subunit 4 were found in plastid RNA, those for the Rieske iron-sulfur protein in cytosolic poly(A) RNA. Transcripts for cytochrome b6 and subunit 4 are translated in rabbit reticulocyte lysates into products of correct length. The Rieske iron-sulfur protein and the cytochrome f apoprotein appear to be made as precursors with excess sequences of 7 and 4 kd, respectively. Cytochrome f, cytochrome b6 and subunit 4 are encoded by uninterrupted plastid genes that are located in the large single-copy region of the circular DNA molecule. Each of these genes is present once per chromosome. Their location and direction of transcription have been determined by hybrid-selection mapping and by cell-free transcription/translation of various recombinant DNAs. The genes for cytochrome b6 and for subunit 4 lie near each other, but do not overlap. They are transcribed into a single message. The gene for cytochrome f maps 15 kbp away from this cluster, close to the 3' end of the gene for the large subunit of ribulosebisphosphate carboxylase/oxygenase, and is transcribed into a separate 4 kb long RNA. All these genes have the same polarities with respect to each other.
authors.affiliation: Botanisches Institut der Universität, Universitätsstr. 1, 4 Düsseldorf 1, FRG.
authors.forename: J
authors.initials: J
authors.lastname: Alt
authors.forename: P
authors.initials: P
authors.lastname: Westhoff
authors.forename: B B
authors.initials: BB
authors.lastname: Sears
authors.forename: N
authors.initials: N
authors.lastname: Nelson
authors.forename: E
authors.initials: E
authors.lastname: Hurt
authors.forename: G
authors.initials: G
authors.lastname: Hauska
authors.forename: R G
authors.initials: RG
authors.lastname: Herrmann