Under the supervision of Prof. P.Balaram.

A large number of antibiotic peptides of fungal origin related to alamethicin have been extensively investigated for their structural and membrane rnodlfylng properties. Alamethicin and related peptides are characterised by a high content of a-aminoisobutyric acid (Aib) residues, posses a C-terminal alcohol residue, are blocked at the N-terminus and are produced in fungal cultures as complex microheterogenous mixtures (Mathew and Balaram, 1983). This family of peptide antibiotics termed peptaibols have proved useful in developing models for peptide channel formation (Sansom, 1993). The efrapeptins are a unique class of Aib containing peptides of fungal origin which contain a strongly basic C-terminus residue, in contrast to the members of the peptaibol family. Efrapeptins ( produced by the fungus Tolypocladium niveum) * a rnicroheterogenous mixture of fifteen residue long hydrophobic peptides(Bullough et al., 1982a), with the N-terminal acetylated and the C- terminal blocked by 1-is0 butyl-2- [ 1-pyrrolo- ( 1,2-a) pyrimidinium-2,3,4,6,7,8-hexhydrolethyla (Gupta et al., 1992) are known to be inhibitors of ATP synthesis. They bind to F1-ATPase(Lardy et al., 1975). They inhibit ATP synthesis in intact mitochondnal FoF1-ATPase and ATP hydrolysis in isolated F1-ATPase(Cross and Kohlbrenner, 1978). The sequence of efrapeptin is: The replacement of the underhed residues Aib by Iva and Gly by Ala results in a microheterogenous mixture of efrapeptins designated efrapeptins C-G. X is the condensation product of Ieucinol an