THE LOCUST NEUROPARSIN-A - SEQUENCE AND SIMILARITIES WITH VERTEBRATE AND INSECT POLYPEPTIDE HORMONES

Neuroparsin A isolated from the nervous corpora cardiaca of Locusta migratoria has been completely sequenced. It is made up of two very similar polypeptide chains linked by disulfide bridges. It exhibits four microheterogeneous N-termini which are produced naturally by post-translational enzymatic reaction: Asn-Pro-Ile-Ser-Arg accounts for 70% of the N-terminal sequences, Ile-Ser-Arg (20%), Ser-Arg (5%) and Arg (5%). The remainder of the molecule is a homodimer identical to neuroparsin B. The longest neuroparsin A (M(w) = 8759 Da) is partially and progressively transformed into neuroparsin B by a stepwise protelysis which is probably arrested at a putative disulfide bridge involving Cys2 in neuroparsin B. In spite of slight similarities with numerous other hormones, computed comparison with other sequences from the literature revealed only a low level of homology for neuroparsin.