Two conformational states in the crystal structure of the Homo sapiens cytoplasmic ribosomal decoding A site.
The decoding A site of the small ribosomal subunit is an RNA molecular switch, which monitors codon-anticodon interactions to guarantee translation fidelity. We have solved the crystal structure of an RNA fragment containing two Homo sapiens cytoplasmic A sites. Each of the two A sites presents a different conformational state. In one state, adenines A1492 and A1493 are fully bulged-out with C1409 forming a wobble-like pair to A1491. In the second state, adenines A1492 and A1493 form non-Watson-Crick pairs with C1409 and G1408, respectively while A1491 bulges out. The first state of the eukaryotic A site is, thus, basically the same as in the bacterial A site with bulging A1492 and A1493. It is the state used for recognition of the codon/anticodon complex. On the contrary, the second state of the H.sapiens cytoplasmic A site is drastically different from any of those observed for the bacterial A site without bulging A1492 and A1493.
Kondo
Jiro
J
Institut de Biologie Moléculaire et Cellulaire, UPR9002 CNRS, Université Louis Pasteur, 15 rue René Descartes, 67084 Strasbourg, France.
Urzhumtsev
Alexandre
A
Westhof
Eric
E
D000818:Animals; D018360:Crystallography, X-Ray; D005815:Genetic Code; D006801:Humans; D008958:Models, Molecular; D009328:Nebramycin / Q000031:analogs & derivatives / Q000737:chemistry; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry; D016053:RNA, Protozoan / Q000737:chemistry; D012336:RNA, Ribosomal, 16S / Q000737:chemistry; D012337:RNA, Ribosomal, 18S / Q000737:chemistry*; D012270:Ribosomes / Q000737:chemistry; D016808:Tetrahymena thermophila / Q000235:genetics
D012329:RNA, Bacterial; D016053:RNA, Protozoan; D012336:RNA, Ribosomal, 16S; D012337:RNA, Ribosomal, 18S; D009328:Nebramycin; C011666:apramycin