Sequence determination secretin

A large amount of information (sequences, agonist and antagonist binding, mutation studies, etc.) is available for the rhodopsin-like G protein-coupled receptors. However, only limited information exists about the secretin-like and metabotropic glutamate receptors, and too few sequences have been determined yet to define sequence-conservation patterns in these subfamilies. Consequently,... 

The contrast between the presence of well defined conformation in secretin and the absence of rigid geometry in bradykinin or CCK pronq>ts the speculation that the cooperative intramolecular interactions which determine the architecture of secretin might be replaced by similar but in-termolecular interactions in CCK (perhaps also in bradykinin), that is by interactions between the hormone and the yet unknown receptor site. Some support for this speculation can be found in the remarkable fact that while with secretin practically the whole chain is needed for full biological activity, this is not true for CCK already relatively short C-terminal sequences reveal the various hormonal activities of the CCK itself. 

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