Volume 6 Issue 4, April 2010

In most archaea, the enzyme TiaS post-transcriptionally modifies a cytidine in the anticodon of tRNA^Ile, converting it to agmatidine (agm²C or C⁺). This unique nucleoside allows translation at the AUA isoleucine codon and prevents misreading of the AUG methionine codon.

Many kinase inhibitors for cancer therapy are rather nonselective, and their cellular mechanisms of action are incompletely understood. A nested chemical proteomics and chemical genetics strategy reveals which cellular targets of the clinical kinase inhibitor dasatinib functionally relate to its anti-oncogenic activity.

The final steps in the biosynthetic pathway to the morphine alkaloids have been revealed with the characterization of two key enzymes. In addition to the widely exploited parent compound, these new O-demethylases control metabolic flux to pharmaceutically useful opioid precursors.

Evolutionary conservation of TRPA1 underlies sensation of reactive noxious chemicals from flies to humans.

A caged version of the neurotransmitter GABA can be activated by two-photon excitation to evoke small, fast GABAergic currents to allow functional mapping of GABA receptor distribution in living brain tissue with single-synapse resolution.

Ru(II)(tris-bipyridyl)²⁺ derivatives photocatalytically generate singlet oxygen. Attaching these ruthenium conjugates to small-molecule inhibitors of intracellular or integral membrane proteins turned modest-potency compounds into chemical knockout reagents that potently inactivated targets in response to light.

Beewolf digger wasps protect their larvae from microbial infestation by cultivating Streptomyces bacteria that produce antimicrobial compounds. A new study uses intact specimens to investigate the placement and production of nine antibiotics that combine to kill a wide range of pathogens.

Bacterial cultures can express proteins in high yields but cannot create mammalian N-glycoforms. Engineering of the glycosylation machinery of C. jejuni and its transfer into E. coli, combined with trimming and rebuilding of the N-linked glycan, now provides a robust route to glycoproteins.

Semisynthetic methods to make ubiquitin conjugates have yielded broad conclusions for epigenetics. A robust intein-mediated chemical crosslinking strategy now expands our understanding by showing that a methyltransferase is surprisingly tolerant of changes to ubiquitin location and composition.

Simple and robust methods to access ubiquitin conjugates are needed to probe the role of this prevalent protein. A new intein-mediated disulfide crosslinking strategy now demonstrates a surprising lack of specificity for the site of ubiquitin labeling in DNA repair.

A plant mutant that fails to accumulate morphine provides a genetic clue to identifying the last two enzymes in this alkaloid biosynthetic pathway. Surprisingly, the proteins are non-heme dioxygenases, thus expanding the range of this versatile class of catalysts.

Ribosomal decoding is dependent on wobble base pairing, which frequently involves modified nucleotides in the tRNA anticodon loop. The discovery of a new guanidine-modified base, 2-agmatinylcytidine, in the tRNA^Ile of archaea uncovers the mechanism for AUA decoding in these organisms.

Profiling of a combinatorial library of post-translationally modified histone H3–based peptides reveals that Thr3 phosphorylation, Arg2 methylation and Thr6 phosphorylation can modulate recognition of Lys4 methylation status by PHD fingers. Additionally, Thr6 phosphorylation, a previously undescribed modification, is shown to exist in native histones.

Determining relevant targets of promiscuous kinase inhibitors has proven difficult. A combination of two mass spectrometry–based proteomic approaches, RNAi depletion and rescue studies with drug-resistant mutants now reveal that SRC, FYN and EGFR are functionally important targets of dasatinib in lung cancer cells.

Asymmetric ADP affinities and dissociation rates as well as optimization of subunit coordination through the long lever arm ensure high processivity under the intramolecular and external off-axis loads that myosin V experiences in vivo.