. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 348 D. A. PRICE ET AL between them are poorly conserved in P. acutangula (Fig. 3). The precursor in this species is only 41% identi- cal to H. aspersa at the nucleotide level, and 34% at the amino acid level. Moreover, although the overall length of the region between the two outside landmarks— pQFYR (I/F) amide and FMRFamide (see Fig. 1)—is exactly the same as for H. aspersa, three off-setting gaps were required to align the tetrabasic and dibasic cleavage sites in the two species. For another example, the peptide just 5' o
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 348 D. A. PRICE ET AL between them are poorly conserved in P. acutangula (Fig. 3). The precursor in this species is only 41% identi- cal to H. aspersa at the nucleotide level, and 34% at the amino acid level. Moreover, although the overall length of the region between the two outside landmarks— pQFYR (I/F) amide and FMRFamide (see Fig. 1)—is exactly the same as for H. aspersa, three off-setting gaps were required to align the tetrabasic and dibasic cleavage sites in the two species. For another example, the peptide just 5' of the tetrabasic site is especially dissimilar to that of H. aspersa: , it is longer (23 amino acids instead of 20) and, even with the gaps, only 17% conserved. Isolation of pQFYRFamide The predicted peptide pQFYRFamide was synthe- sized; it was as reactive as FMRFamide in an RIA with antiserum S253 which facilitated the purification. The synthetic peptide eluted at 12-13 min in the TFA/ACN solvent system, coincident with a large peak of im- munoreactivity observed with H. aspersa ganglion ex- tracts (see Price et al., 1990, for a typical pattern). Since this large peak also contains SDPFLRFamide and NDP- FLRFamide, we sought a second solvent system that could separate pQFYRFamide from these two heptapep- tides; the phosphate/ACN system proved to be satisfac- tory. This fractionation procedure, with one modification, was applied separately to two H. aspersa extracts, one made from 50 pairs of cerebral ganglia and another from 30 subesophageal ganglia. The cerebral ganglion extract was given a preliminary fractionation with the HFBA/ ACN system. Thereafter, each extract was fractionated on a TFA/ACN gradient, and the immunoreactive peaks from this run were further resolved with the phosphate/ ACN solvent system. On this system, the cerebral gan- glion extract showed a large peak at 19 min corresponding to synthetic pQFYRFamide, and a small peak at 16 min correspond
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