Factors in a chloroplast extract specifically bind to the 5' untranslated regions of chloroplast mRNAs.

The spinach chloroplast large ATP synthase cluster encodes five genes, the last four of which encode chloroplast ATP synthase subunits. Because the stoichiometry of the ATP synthase polypeptide products differs substantially from that of the primary transcripts, we have chosen this system as a model to study posttranscriptional mechanisms that regulate chloroplast gene expression. Here we present data on a chloroplast extract containing factors that bind to the 5' untranslated regions of chloroplast ATP synthase transcripts. The binding is transcript-specific. This binding may influence translational efficiency of chloroplast transcripts.