P. Heino et al., Binding of CGRP analogs and their effect on adenylate cyclase activity in porcine iris-ciliary body, J OCUL PH T, 14(6), 1998, pp. 543-554
The structure-activity relationship of the calcitonin gene-related peptide
(CGRP) in the porcine iris-ciliary body was studied using different CGRP an
alogs. The receptor binding affinity is located mainly in the carboxytermin
al end of the CGRP peptide while the ability to stimulate adenylate cyclase
(AC) enzyme is mainly in the aminoterminal end of the peptide. The binding
of CGRP analogs was also found to be temperature-dependent. Changes in the
alpha-helical region or in the beta-turn, as well as replacements of threo
nine-4, asparagine-25 or asparagine-26, reduce the binding affinity already
at +4 degrees C. Truncated aminoterminus, changes in the loop region betwe
en cysteines 2 and 7, and especially in threonine 6, have for their part an
important role in maintaining AC-stimulating activity.