Theoretical conformational analysis of Asn1, Val5 angiotensin II

A theoretical analysis of the conformation of the octapeptide hormone Asn¹, Val⁵ angiotensin II has been carried out by semiempirical potential energy calculations. A preliminary study of the Ala₆-Pro-Ala molecule, which mimics the angiotensin backbone, provided us with likely backbone structures on which the effect of the full side chains of the hormone could be assessed. For angiotensin II, the calculations show that only a small number of folded, compact conformations have a high probability of existence. This is the consequence of favorable packing and of the presence of proline in position 7. These results are consistent with various experimental data, both structural and biological. This method is readily applicable to the study of analogs of the hormone or to other peptides of comparable size.