Abstract of the PDB Structure's related Publication:
Eukaryotic ribosomes are synthesized in a hierarchical process driven by a plethora of assembly factors, but how maturation events at physically distant sites on pre-ribosomes are coordinated is poorly understood. Using functional analyses and cryo-EM, we show that ribosomal protein Rps20 orchestrates communication between two multi-step maturation events across the pre-40S subunit. Our study reveals that during pre-40S maturation, formation of essential contacts between Rps20 and Rps3 permits assembly factor Ltv1 to recruit the Hrr25 kinase, thereby promoting Ltv1 phosphorylation. In parallel, a deeply buried Rps20 loop reaches to the opposite pre-40S side, where it stimulates Rio2 ATPase activity. Both cascades converge to the final maturation steps releasing Rio2 and phosphorylated Ltv1. We propose that conformational proofreading exerted via Rps20 constitutes a checkpoint permitting assembly factor release and progression of pre-40S maturation only after completion of all earlier maturation steps.
SceRsmA (formerly Dim1p) dimethylates two adjacent A (positions 1779 and 1780; 1518 and 1519 in E. coli numberings) in the loop of a conserved hairpin h45 near the 3′-end of 18S rRNA. AdoMet is the methyl group donor. RsmA can bind on naked rRNA but the target bases cannot be methylated before a subset of ribosomal proteins have bound. Dim2p could be a cofactor. Bacterial RsmA (KsgA) is the ortholog of yeast RsmA (Dim1p). They belong to the erm family of methyltransferases responsible for erythromycin resistance. RsmA homologs exists also Archaea. Notice, the acronym RsmA has also been used for for Regulator of Secondary Metabolism A, a protein not related to the RNA small subunit Methyltransferase.