Comparison of the binding modes of TT-232 in somatostatin receptors type 1 and 4

The somatostatin analogue cyclopeptide TT-232 was docked to homology models of somatostatin receptors type 1 and 4. Calculations have been performed by applying H-bonding (subtype 1: Asp137-Lys5, Gln291- DPhe1, Gln291-Cys2; subtype 4: Asp122-Lys5) and distance (subtype 4: His294-Thr7) constraints with the GOLD docking procedure. Docking showed overlapping TT-232 backbone residues. Differences were found, however, in the position of aromatic amino acids DTrp4, DPhe1 and Tyr3 of TT-232, allowing for different binding modes and functions to be performed by somatostatin receptors type 1 and 4. In accordance, TT-232 did not affect basal GABA release associated with somatostatin receptor type 1 function.