Key result
C-terminal carboxylate ionic interaction mediates angiotensin binding, with ester analogues retaining only ~13% pressor activity.
Ionic carboxylate requirement informs angiotensin analogue design; leaves open stable mimics for therapeutic translation.
[Ac-Asn1, Val5]angiotensin II analogues containing a C-terminal alcohol (Phe-ol), methyl ketone (Pmk), methyl ester (Phe-OMe), or alpha-methyl methyl ester (Phe(alpha Me)-OMe) were prepared in order to examine the relative importance of COOH-mediated ionic vs. hydrogen bonding interactions in angiotensin activities. Based on the observation that only [Ac-Asn1,Phe-OMe8]AII (AII, angiotensin II) had significant activities (20% oxytocic and 13% pressor) in the rat, with all other analogues having negligible agonistic and antagonistic effects, it is concluded that ionic interaction of the C-terminal carboxylate with the receptor is necessary for angiotensin binding and that hydrogen bonding has little effect. Thus, the different potencies observed for the AII methyl ester and for various C-terminal analogues previously reported may simply reflect their relative abilities to generate the active carboxylate species in situ.
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Hsieh et al. (1986) studied this question. Angiotensin II analogues was evaluated on Oxytocic and pressor activities. Ionic interaction of the C-terminal carboxylate with the receptor is necessary for angiotensin binding, as only the methyl ester analogue showed significant oxytocic (20%) and pressor (13%) activities.
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