Structure-contractile activity relationships of neurokinin A on guinea pig tracheal smooth muscle

Abstract

In order to investigate the effect of the fourth and seventh positions from the C-terminus of NKA and NKA(4-10) in biological activity, NKA, NKA(4- 10) and their analogues substituted with the other amino acid residues at these positions were synthesized by solid phase peptide synthesis. The contractile activities of these synthetic peptides on guinea pig tracheal smooth muscle known as the NK-2 receptor-specific tissue, were examined. Our results indicated that the aliphatic amino acid (Val or Ile) and acidic amino acid (Asp) at the fourth and seventh positions from the C-terminus of NKA, respectively, are important for the binding with the NK-2 receptor present in the guinea pig trachea. In particular, the aliphaticity at the fourth position from C-terminus of NKA rather than the hydrophobicity is important for the NK-2 receptor binding affinity.