Inhibition of bacterial RNA polymerase by the cyanobacterial metabolites 12- epi -hapalindole E isonitrile and calothrixin A

Abstract

The alkaloid 12-epi-hapalindole E isonitrile, from a cyanobacterial Fischerella species, and the indolophenanthridine calothrixin A, from Calothrix, inhibited Escherichia coli RNA polymerase competitively with respect to ATP, and non-competitively with respect to UTP. The inhibition was dependent on the order of addition of the inhibitors. The KI values, with ATP as the variable substrate, were 1.3±0.2 mM and 0.23±0.11 mM, respectively. Based on comparisons with the sensitivity of whole cells to these inhibitors, it is concluded that other targets in addition to RNA polymerase may also be implicated in their action. Show more