期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1993
卷号：90
期号：20
页码：9581-9585
DOI：10.1073/pnas.90.20.9581
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The sarcin/ricin loop is a highly conserved sequence found in the RNA of all large ribosomal subunits. The cytotoxins alpha-sarcin and ricin both inactivate ribosomes by cleaving a single bond in that loop. Once it has been attacked, ribosomes no longer interact with elongation factors properly, and translation stops. We have determined the conformation of the sarcin/ricin loop by multinuclear NMR spectroscopy using E73, a 29-nucleotide RNA that has the sarcin/ricin loop sequence and that is sensitive to both toxins in vitro. The sarcin/ricin loop has a compact structure that contains several purine.purine base pairs, a GAGA tetraloop, and a bulged guanosine adjacent to a reverse Hoogsteen A.U pair. It is stabilized by an unusual set of cross-strand base-stacking interactions and imino proton to phosphate oxygen hydrogen bonds. In addition to having interesting structural features, this model explains many of the biochemical observations made about the loop's structure and its reactivity with cytotoxins, and it sheds light on the loop's interactions with elongation factors.
