Sublethal cadmium exposure in the freshwater snail Lymnaea stagnalis meets a deficient, poorly responsive metallothionein system while evoking oxidative and cellular stress.

The Great Pond snail Lymnaea stagnalis (Gastropoda, Hygrophila) is a wide-spread freshwater gastropod, being considered as a model organism for research in many fields of biology, including ecotoxicology. The aim of the present study was to explore the Cd sensitivity of L. stagnalis through the measurement of a biomarker battery for oxidative, toxic and cellular stress.

Unwinding the twister ribozyme: from structure to mechanism.

The twister ribozyme motif has been identified by bioinformatic means very recently. Currently, four crystal structures with ordered active sites together with a series of chemical and biochemical data provide insights into how this RNA accomplishes its efficient self-cleavage. Of particular interest for a mechanistic proposal are structural distinctions observed in the active sites that concern the conformation of the U-A cleavage site dinucleotide (in-line alignment of the attacking 2'-O nucleophile to the to-be-cleaved PO5' bond versus suboptimal alignments) as well as the presence/absence of Mg ions at the scissile phosphate.

In-line alignment and Mg²⁺ coordination at the cleavage site of the env22 twister ribozyme.

Small self-cleaving nucleolytic ribozymes contain catalytic domains that accelerate site-specific cleavage/ligation of phosphodiester backbones. We report on the 2.9-Å crystal structure of the env22 twister ribozyme, which adopts a compact tertiary fold stabilized by co-helical stacking, double-pseudoknot formation and long-range pairing interactions.