THE CYANOBACTERIAL GENOME CONTAINS A SINGLE-COPY OF THE FFH GENE ENCODING A HOMOLOG OF THE 54 KDA SUBUNIT OF SIGNAL RECOGNITION PARTICLE

Cyanobacteria possess thylakoid membranes that differ in their protein composition from the cytoplasmic membrane. To study possible pathways of protein targeting to these membranes, we have investigated whether or not cyanobacteria have a homologue or homologues of the signal rec ognition particlelike chaperone Ffh. We have amplified a fragment of f fh by polymerase chain reaction and established that ffh is present as a single copy in the genomes of three cyanobacterial species. We have cloned and sequenced ffh from Synechococcus sp. PCC7942 and predict t hat Ffh functions as a ribonucleoprotein in cyanobacteria and chloropl asts.