Bacterial orthologues indicate the malarial plastid gene ycf24 is essential

ycf24 is a well conserved gene found in all major groups of bacteria, as we ll as on red algal plastid genomes and the vestigal plastid genome of apico mplexan pathogens like the malaria parasite Plasmodium falciparum (ORF470). Some database annotations describe Ycf24 as an ABC transporter subunit, bu t we find the level of significance is low. To investigate ycf24's function we disrupted it in the cyanobacterium Synechocystis sp., strain PCC6803 wh ich has a multi-copy genome. This showed ycf24 is essential, partial loss p roducing a terminal phenotype of chlorosis, reduced cell size, loss of DNA, and a striking arrest in cytokinesis, Attempts to disrupt the single copy of ycf24 in E. coli failed to give stable transformants. When Ycf24 was ove r-expressed in E. coli as a soluble fusion protein, it localized mostly as a band on either side of the nucleoid and nucleoid partitioning was aberran t. We propose the relict plastid organelle of apicomplexans retains its cap acity for protein synthesis because Ycf24 is essential.