Ribosome-binding factor involved in light- and temperature-dependent control of protein synthesis. Interacts with 16S sRNA nucleotides at the A-site and P-site, where it protects the decoding center and inhibits translation by preventing tRNA binding. Stabilizes 70S ribosomes against dissociation. May be recycled by the combined action of ribosome-recycling factor (RRF) and EF-G. Binds to the mRNA channel of the chloroplast small ribosomal subunit and interacts with 16S sRNA nucleotides at the A-site and P-site. Belongs to the HPF/YfiA ribosome-associated protein family. Long plastid HPF subfamily. Was originally (PubMed:2693942, PubMed:2259340, PubMed:2376575, PubMed:1731992, PubMed:10874039, PubMed:18042701) thought to be a ribosomal protein.