. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. THE STRUCTURE OF A FISH BRAIN ANP 283. 500 1000 1500 2000 2500 3000 m/z 5 iuu • 100i Monoisotopic Protonated Theoretical Molecular Ion \ Ion Distribution 80- Calculated \ C99 H158N31°29S3 0} Observed o 50 c 03 -o 60- 13 .Q 0> = 40- 0 ' ' ' ' ' ^ 2350 re rr 20- |ll II II Ih 2300 3220 2340 2360 2380 240 m/z Figure 4. Positive ion FAB mass spectrum of the purified, mildly oxidized peak. A. Scan up to 3000 nominal mass. In the inset the x-axis is unchanged, but the y-axis is expanded 10-fold. The masses shown ar
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. THE STRUCTURE OF A FISH BRAIN ANP 283. 500 1000 1500 2000 2500 3000 m/z 5 iuu • 100i Monoisotopic Protonated Theoretical Molecular Ion \ Ion Distribution 80- Calculated \ C99 H158N31°29S3 0} Observed o 50 c 03 -o 60- 13 .Q 0> = 40- 0 ' ' ' ' ' ^ 2350 re rr 20- |ll II II Ih 2300 3220 2340 2360 2380 240 m/z Figure 4. Positive ion FAB mass spectrum of the purified, mildly oxidized peak. A. Scan up to 3000 nominal mass. In the inset the x-axis is unchanged, but the y-axis is expanded 10-fold. The masses shown are rounded to the nearest integer. The two labeled ion clusters are the singly and doubly protonated molecular ions. B. The mass region around 2342, expanded to show the singly protonated molecular ion cluster. The theoretical ion distribution expected for a compound with the elemental composition found is shown in the inset. ilar to an ANP isolated from eel heart (2 amino acid differences), and both fish peptides are quite similar to a peptide isolated from porcine brain (3 differences within the ring; Fig. 5). The complete absence of a C-terminal "tail" is a unique feature not previously reported for any natri- uretic peptide. The FABms data establish that the pep- tide sequenced had no tail, but we cannot completely rule out the possibility that a tail was lost by proteolysis during purification. Such degradation is unlikely, how- ever, because the retention time of the immunoreactive peak remains the same when extracts are prepared in other ways (data not shown), and Y. Takei (pers. comm.) has sequenced an eel brain ANP-like peptide that also has no tail. Still, this question will not be settled until the cDNA encoding the precursor has been isolated. The C-terminal tail seems to be irrelevant to either the relaxing activity of the peptide or its immunoreactivity. Thus, synthetic killifish peptide and eel ANP (which has a C-terminal tail) are equipotent in relax
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
