ChemBioChem

June 14, 2013

ChemBioChem 9/2013 Fine-tuning protein stability

Rubini and co-workers have created a thioredoxin analogue (Trx1P) containing a single cis-proline residue by replacing the trans-proline residues with alanine. In their Communication, the authors show that the non-natural amino acids (2S,4R)- and (2S,4S)-fluoroproline ((4R)-Flp and (4S)-Flp) could be quantitatively incorporated into Trx1P. An endo conformation of the Pro pyrrolidine ring was found in both fluoroproline stereoisomers, although (4R)-Flp usually favors the exo conformation. This indicates that the tertiary structure directs the Flp ring conformation and the Pro-to-Flp substitutions give the potential for modulating the stability of proteins without changing their biological activity.

In another Communication, Bhabak et al. describe two complimentary doubly labeled ceramides, each of them carrying 7-nitrobenz-2-oxa-1,3-diazole (NBD) as donor and Nile Red (NR) as acceptor fluorophores. Both substrates were treated with acid and neutral ceramidases and shown to be effective FRET probes for the real-time determination of ceramidase activity. The ceramide analogue with NBD attached to the fatty acid moiety and NR to the sphingosine part showed larger spectral changes and has the potential to be used as an in situ probe in living cells.

Aurachin RE, first identified in the genus Rhodococcus, is a farnesylated quinoline antibiotic active against other Gram-positive bacteria. Now, in a Full Paper, Kitagawa et al. present the heterologous expression of the gene cluster controlling aurachin RE biosynthesis. This cluster contains genes that encode, among others, a prenyltransferase, polyketide synthase, and notably, a cytochrome P450 (RauA). Disruption of the rauA gene led to accumulation of an aurachin lacking the N-hydroxyl group that is crucial for antibacterial activity. Identification of this P450 suggests a convergent evolution of unrelated Stigametlla species that instead use a Rieske oxygenase to produce aurachins.

This issue also contains, among others, notable contributions from Nicola Brasch (Kent State University), Christy Landes (Rice University) and R. Jeremy Johnson (Butler University). Browse Issue 9/2013 now.

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