High-affinity binding of [3H]neuropeptide Y to a polypeptide from the venom of Conus anemone

Molecular characterization of the high-affinity [3H]neuropeptide Y-binding component from the venom of Conus anemone

The venom of the marine snail Conus anemone contains the 'ANPY toxin' which binds neuropeptide Y (NPY) and related insect peptides with nanomolar affinity. This toxin has initially been proposed to be a major 18.5 kDa component of the venom. Here we demonstrate that the 18.5 kDa proteins of venom produce at least five different bands in native electrophoresis and that none of them binds [3H]NPY. Instead, the ANPY toxin migrates as a distinct band on native electrophoresis and is only present as a minor component in the venom. Its approximate molecular weight is 17.5 kDa and its [3H]NPY binding activity is extremely stable below 37 degrees C, even in the absence of protease inhibitors.

Formation of angiotensin-(1-7) from angiotensin II by the venom of Conus geographus

The binding of [3H]angiotensin II to AT(1) receptors on Chinese Hamster Ovary cells expressing the human AT(1) receptor (CHO-AT(1) cells) is potently inhibited by venoms of the marine snails Conus geographus and C. betulinus. On the other hand, the binding of the nonpeptide AT(1) receptor-selective antagonist [3H]candesartan is not affected but competition binding curves of angiotensin II and the peptide antagonist [Sar(1),Ile(8)]angiotensin II (sarile) are shifted to the right. These effects resulted from the breakdown of angiotensin II into smaller fragments that do not bind to the AT(1) receptor. In this context, angiotensin-(1-7) is the most prominent fragment and angiotensin-(1-4) and angiotensin-(1-5) are also formed but to a lesser extent. The molecular weight of the involved peptidases exceeds 50 kDa, as determined by gel chromatography and ultrafitration.

High affinity displacement of [(3)H]NPY binding to the crude venom of conus anemone by insect neuropeptides

The venom from Conus anemone contains a protein, named ANPY toxin, which displayed high affinity (IC(50) in nanomolar range) to neuropeptide Y (NPY), [Leu(31), Pro(34)]NPY, peptide YY, pancreatic polypeptide, the Y(1) antagonist 1229U91, and C-terminal NPY fragments. N-terminal fragments and the free acid form of NPY did not bind to ANPY. The truncated NPY fragments displayed very low affinity to Y(1) receptors and partially inhibited [(3)H]NPY binding to anti-NPY antiserum. Several insect neuropeptides, the sequences of which related to the C-terminal fragments of NPY, were observed to bind with similar affinity or even 20 times higher (Lom-MS and Scg-NPF) affinity than NPY. In contrast, no significant binding of these insect peptides was observed for Y(1) receptors and anti-NPY antiserum. Therefore, ANPY can be viewed as an acceptor that binds with very high affinity to a broad spectrum of vertebrate and invertebrate neuropeptides that share a similar C-terminal amino acid sequence.