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Science 22 September 2006:
Vol. 313. no. 5794, p. 1700
DOI: 10.1126/science.313.5794.1700a
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This Week in Science
It has been suggested that self-cleaving RNAs and other ribozymes represented a step--the RNA world--in the origin of life (see the Perspective by Been). Now Klein and Ferré-D'Amaré (p. 1752) report crystal structures of the glmS ribozyme, which regulates the synthesis of glucosamine-6-phosphate (GlcN6P), a key metabolic precursor of the bacterial cell wall. The structures cover the precleavage state, both unbound and bound to the competitive inhibitor glucose-6-phosphate, and the postcleavage state. Unlike other riboswitches, where metabolite binding regulates activity by inducing a conformational change, in GlmS the ribozyme conformation is similar in all three states. GlcN6P binds to a preformed site and is precisely positioned to serve as a coenzyme. Few self-cleaving ribozymes have been detected in mammals, leading to speculation that they have been lost over evolution. Salehi-Ashtiani et al. (p. 1788) identified a self-cleaving ribozyme in the human genome that shares biochemical and structural properties with hepatitis delta virus ribozymes.
CREDIT: KLEIN AND FERRÉ-D'AMARÉ |
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Science. ISSN 0036-8075 (print), 1095-9203 (online)
