Volume 3 Issue 11, November 2007

There is a gap between the nanoscale level of molecular structure and the micron-sized level of cellular ultrastructure that is difficult to probe experimentally. New techniques and simulated images are revealing its secrets.

By questioning the very nature of how ion channels, brains and societies form and function, Nobel laureate Jean-Marie Lehn has changed our understanding of the chemical basis of self-organization.

Nitric oxide–mediated production of cyclic guanosine 3′,5′-monophosphate (cGMP) is a crucial signal transduction pathway that controls a wide array of biological functions. A new layer of complexity in mammalian cell regulation is revealed by the discovery of a redox-active nitrated cGMP derivative with the ability to post-translationally modify protein thiol residues by S-guanylation.

A phosphorothioate modification of DNA has been identified in bacteria. This first observed alteration of the DNA phosphate backbone opens many questions about the mechanism of sulfur incorporation and the function of this modification.

The C₁₂ 'earthy' odorant geosmin is derived from the C₁₅ metabolite farnesyl diphosphate. Metabolic transformation now seems to be catalyzed by a bifunctional protein having two operatively independent sesquiterpene synthase domains. The domains are catalytically linked through the passive diffusion of a C₁₅ alcohol product of the N-terminal catalytic domain to the C-terminal catalytic domain for the final steps of geosmin formation.

An emerging view is that high-fidelity metal selection by the proteins involved in metal homeostasis is pivotal to ensure that the correct metals bind to nascent metalloproteins. A new study demonstrates that the AztA zinc exporter performs this function by using tandem metal-binding domains to entrap some of the wrong metals in nonproductive complexes.

A recently characterized 'M-box' genetic switch from bacteria is proposed to directly sense cellular Mg²⁺ levels through the conformation of its newly synthesized RNA. This Mg²⁺-sensing riboswitch controls transcription termination in front of a Mg²⁺ transporter gene, thus introducing a new and direct level of genetic regulation to metal ion homeostasis.