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General acid catalysis by a ribozyme. Das & Piccirilli show (p 45) that a hepatitis delta virus ribozyme uses a cytosine nucleobase as a general acid catalyst of phosphodiester bond cleavage (see also News & Views by Strobel, p 5). Cover art by Lewis Long, watercolor and ink on paper.
Ribozymes are enzymes comprised of RNA that fold into three-dimensional structures and that catalyze chemical reactions central to all cells. A new study shows that ribozymes, like proteins, may use general acid catalysis as part of their catalytic toolkit.
Nitric oxide signaling requires that the heme of soluble guanylate cyclase bind NO preferentially to O2. Engineering of the enzyme's active site reveals a molecular basis for NO binding selectivity.
ComX is a post-translationally modified peptide involved in quorum sensing in Bacillus subtilis. The structure of ComX has now been shown to contain a geranylated tryptophan with an unusual tricyclic architecture.
The fate of cells depends on a delicate balance of pro- and anti-apoptotic proteins. Small-molecule inhibitors of anti-apoptotic protein-protein interactions promote apoptosis in cancer cells.