Inhibition of RNA polymerase by streptolydigin: no cycling allowed

Stereoselective Synthesis of Benzoylated Gulmirecin A and Disciformycin B

Disciformycins and gulmirecins are potent inhibitors of the bacterial RNA polymerase. They show promising activities against multidrug-resistant pathogens often found in clinical settings, such as methicillin- and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA). Our modular, high-yielding, and scalable synthetic approach started with the desymmetrization of divinyl carbinol and provided benzoylated precursors for both natural product classes. The 12-membered macrocycle was assembled by a stereoselective Nozaki-Hiyama-Takai-Kishi macrocyclization.

Pleomorphic effects of three small-molecule inhibitors on transcription elongation by Mycobacterium tuberculosis RNA polymerase

The Mycobacterium tuberculosis RNA polymerase (MtbRNAP) is the target of the first-line anti-tuberculosis inhibitor rifampin, however, the emergence of rifampin resistance necessitates the development of new antibiotics. Here, we communicate the first single-molecule characterization of MtbRNAP elongation and its inhibition by three diverse small-molecule inhibitors: N(α)-aroyl-N-aryl-phenylalaninamide (D-IX216), streptolydigin (Stl), and pseudouridimycin (PUM) using high-resolution optical tweezers. Compared to Escherichia coli RNA polymerase (EcoRNAP), MtbRNAP transcribes more slowly, has similar mechanical robustness, and only weakly recognizes E. coli pause sequences. The three small-molecule inhibitors of MtbRNAP exhibit strikingly different effects on transcription elongation. In the presence of D-IX216, which inhibits RNAP active-center bridge-helix motions required for nucleotide addition, the enzyme exhibits transitions between slowly and super-slowly elongating inhibited states. Stl, which inhibits the RNAP trigger-loop motions also required for nucleotide addition, inhibits RNAP primarily by inducing pausing and backtracking. PUM, a nucleoside analog of UTP, in addition to acting as a competitive inhibitor, induces the formation of slowly elongating RNAP inhibited states. Our results indicate that the three classes of small-molecule inhibitors affect the enzyme in distinct ways and show that the combination of Stl and D-IX216, which both target the RNAP bridge helix, has a strong synergistic effect on the enzyme.

Biosynthesis of streptolydigin: origin of the oxygen atoms

[Structure: see text] Biosynthetic incorporations of [13C,18O]-labeled precursors into streptolydigin reveal the origin of the oxygen atoms, limiting the possible pathways for acyltetramic acid ring assembly and for formation of the bicyclic ketal.

Progress in targeting bacterial transcription

The bacterial RNA polymerase (RNAP) is an essential enzyme that is responsible for making RNA from a DNA template and is targeted by several antibiotics. Rifampicin was the first of such antibiotics to be described and is one of the most efficient anti-tuberculosis drugs in use. In the past five years, structural studies of bacterial RNAP and the resolution of several complexes of drugs bound to RNAP subunits have revealed molecular details of the drug-binding sites and the mechanism of drug action. This knowledge opens avenues for the development of antibiotics. Here these drugs are reviewed, together with their mechanisms and their potential interest for therapeutic applications.