Recently, Murray et al. (Chem Biol, 1998, 5:587-595) found that the hammerhead ribozyme does not require divalent metal ions for activity if incubated in high (> or =1 M) concentrations of monovalent ions. We further characterized the hammerhead cleavage reaction in the absence of divalent metal. The hammerhead is active in a wide range of monovalent ions, and the rate enhancement in 4 M Li+ is...

The structures of isolated alkaline earth metal cationized amino acids are investigated using infrared multiple photon dissociation (IRMPD) spectroscopy and theory. These results indicate that arginine, glutamine, proline, serine, and valine all adopt zwitterionic structures when complexed with divalent barium. The IRMPD spectra for these ions exhibit bands assigned to carboxylate stretching mo...

The hepatitis delta virus (HDV) ribozyme catalyzes viral RNA self-cleavage through general acid-base chemistry in which an active-site cytidine and at least one metal ion are involved. Monovalent metal ions support slow catalysis and were proposed to substitute for structural, but not catalytic, divalent metal ions in the RNA. To investigate the role of monovalent cations in ribozyme structure ...

the present ")Cd n.m.r. data suggest that phospholipase C contains three classes of metal binding site. Type I, which is a single site buried somewhat in the structure, has a marked preference for Zn2+. This site has the highest affinity for divalent metal ions. Type I1 is a single site of somewhat lower affinity for divalent metal ions and shows a lesser preference for Zn2+ than the type I sit...

Lethal Toxin from Clostridium sordellii (TcsL) and Toxin B from Clostridium difficile (TcdB) belong to the family of the "Large clostridial glycosylating toxins." These toxins mono-O-glucosylate low molecular weight GTPases of the Rho and Ras families by exploiting UDP-glucose as a hexose donor. TcsL is casually involved in the toxic shock syndrome and the gas gangrene. TcdB-together with Toxin...

Escherichia coli ribonuclease III (RNase III; EC 3.1.24) is a double-stranded(ds)-RNA-specific endonuclease with key roles in diverse RNA maturation and decay pathways. E.coli RNase III is a member of a structurally distinct superfamily that includes Dicer, a central enzyme in the mechanism of RNA interference. E.coli RNase III requires a divalent metal ion for activity, with Mg2+ as the prefer...

The factors influencing the oligomerization state of OXA-10 and OXA-14 class D beta-lactamases in solution have been investigated. Both enzymes were found to exist as an equilibrium mixture of a monomer and dimer, with a K(d) close to 40 microM. The dimeric form was stabilized by divalent metal cations. The ability of different metal ions to stabilize the dimer was in the following order: Cd(2+...

RNAs that undergo a rapid site-specific cleavage at low pH have been selected by in vitro selection (the SELEX process). The cleavage does not require the addition of any divalent metal ions, and is in fact inhibited by divalent metal ions, spermine, or high concentrations of monovalent metal ions. This low pH catalyzed cleavage results in a 2',3'-cyclic phosphate at the 3' end and a free hydro...

The hairpin ribozyme comprises two formally unpaired loops carried on two arms of a four-way helical RNA junction. Addition of divalent metal ions brings about a conformational transition into an antiparallel structure in which there is an intimate association between the loops to generate the active form of the ribozyme. In this study, we have used fluorescence resonance energy transfer to ana...

The hepatitis C (HCV) internal ribosome entry site (IRES) element plays a central role in cap-independent translation of the viral genomic RNA. The unique conformation of IRES domain II is critical for 80S ribosomal assembly and initiation of viral translation. Here, the crystal structure of subdomain IIa of the HCV IRES has been determined at 2.3 A resolution, revealing the positions of divale...