Structure of the yeast ribosomal 5 S RNA-binding protein YL3.

A gene coding for the 5 S rRNA-binding protein (YL3) in yeast (Saccharomyces cerevisiae) was isolated using a polymerase chain reaction-amplified gene probe. The DNA sequence contains no introns and codes for a 297 amino acid (Mr = 33,741) protein. Although the protein is just 1 residue longer than in rat, unlike the high sequence homology in the 5 S rRNAs from the same organisms, only about 45% of the amino acid residues are conserved with surprisingly little homology in the carboxyl-terminal end. Nevertheless, comparative studies indicate that a number of structural features are conserved including small repeats in the primary structure and a number of helical estimates in the higher order structure. One of the sequence repeats also appears to be present in the carboxyl-terminal end of the eukaryotic transcription factor TFIIIA suggesting an evolutionary relationship in these 5 S RNA-binding proteins.