BIOLOGICAL FUNCTION OF GRAMICIDIN .3. COMPARISON OF THE EFFECT OF LINEAR GRAMICIDIN ANALOGS ON BACTERIAL SPORULATION, MEMBRANE-PERMEABILITY, AND RIBONUCLEIC-ACID POLYMERASE

Various analogues of linear gramicidin were tested for their biological activity in restoring the normal spore phenotype of gramicidin-negative mutants of BacIIIus brevis and for their ability to increase cation conductivity of black lipid membranes and to inhibit bacterial RNA polymerase. Whereas many biologically active gramicidin analogues had no effect on membrane permeability, all biologically active peptides were able to inhibit ribonucleic acid (RNA) polymerase. These observations make it unlikely that membranes are the site of action of gramicidin during bacterial sporulation, but they are consistent with the notion that gramicidin functions to control RNA synthesis during the transition from vegetative growth to sporulation (Sarkar & Paulus, 1972). The relationship between peptide structure and the ability to restore normal sporulation and inhibit RNA polymerase showed that the eight amino-terminal residues have little influence on the function of gramicidin, whereas the highly nonpolar repeating sequence d-leucyl-l-tryptophan is essential for biological activity and may represent the site of interaction with RNA polymerase. © 1979, American Chemical Society. All rights reserved.