Inhibition of RNA Polymerase by Streptolydigin: No Cycling Allowed

Bacterial RNA polymerase is a common target for many antibiotics. In two recent papers in Cell and Molecular Cell, Tuske et al. (2005) and Temiakov et al. (2005) describe a structural basis for inhibition of bacterial RNA polymerase by the antibiotic streptolydigin. Streptolydigin may prevent distortion of a “bridge” α helix postulated to occur during the nucleotide addition cycle of RNA polymerase or may block a small movement of the bridge helix that helps load nucleotide triphosphates into the active site.