Isolation and chemical characterization of a novel insulin-related neuropeptide from the freshwater snail, Lymnaea stagnalis. |
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Authors: | K W Li W P Geraerts |
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Affiliation: | Faculty of Biology, Vrije Universiteit, Amsterdam, The Netherlands. |
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Abstract: | A novel molluscan insulin-related peptide (MIP) III, has been isolated from alcohol extracts of the neurohaemal area of the cerebral neuroendocrine light-green neurones of Lymnaea stagnalis. MIP III was purified by sequential high-performance gel-permeation chromatography followed by reverse-phase HPLC. MIP III is a heterodimer connected by disulphide bonds. Edman degradation analysis and subsequent alignment with the A and B chains of the previously identified MIP I and II showed that the 24-amino-acid peptide with the sequence pQSRPSIVC(E)CCFNQCTVQ(E)LLAYC represents the MIP III A chain, and the 37-amino-acid peptide sequence TTQHTCSILSRPHPRGLCGSTLANMVQWLCSTYTTSS the B chain. The overall amino acid sequence of MIP III shows about 50% similarity with those of MIP I and II, and only 20-40% similarity with other peptides of the insulin superfamily. Important structural features, e.g. disulphide bridges and the hydrophobic core, are conserved in MIP III. |
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