Volume 10 Issue 1, January 2003

Protein toxins are known to translocate through intracellular membranes to reach their cytosolic targets. Results from studies with botulinum neurotoxin suggest that the toxin heavy chain functions as both a channel and a chaperone for translocation of the catalytically active light chain.

Dipeptidyl peptidase IV contributes to the regulation of many physiological processes, most notably blood sugar homeostasis, by biting a dipeptide off the N terminus of specific peptides. A structure of this peptidase in complex with an inhibitor will assist efforts to regulate this regulator.

Dinucleotide CA repeats of variable length in an intron of the human endothelial nitric oxide synthase gene act as regulatory signals for splicing of the gene's pre-mRNA. Repeat length–dependent binding of hnRNP L to the repeats provides an intriguing link between splicing efficiency, nitric oxide synthesis and cardiovascular disease.

The hormone-related protein PTHrP travels from the cytosol to the nucleus by binding to the transport factor importin β. Remarkably, the site of recognition of PTHrP is the N-terminal half of importin β, which also has Ran-binding and nucleoporin-binding capabilities and is, therefore, sufficient by itself to function in PTHrP nuclear import.

In eukaryotes, newly manufactured mRNA is subject to strict quality control. If certain standards are not met, offending messages are retained in the nucleus and degraded by the exosome complex. New data suggest that exosome-mediated processes are intimately coupled to the transcription machinery, which makes the mRNA in the first place.