. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Log [Nucleotide] (M) Figure 11. Nucleotide effects on solubilized receptors. The specific binding of nM radioligand to solubilized SQM was determined in two independent experiments with the nucleotides GTP. GTP[-y]S and ATP. The percentage of control specific binding (mean ± SEM) has been plotted against nucleotide concentration. were linearly related to those determined with the mem- brane-bound receptors, and the slope was unity (Fig. 13). This finding suggests that the binding specificities of the two preparations we
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Log [Nucleotide] (M) Figure 11. Nucleotide effects on solubilized receptors. The specific binding of nM radioligand to solubilized SQM was determined in two independent experiments with the nucleotides GTP. GTP[-y]S and ATP. The percentage of control specific binding (mean ± SEM) has been plotted against nucleotide concentration. were linearly related to those determined with the mem- brane-bound receptors, and the slope was unity (Fig. 13). This finding suggests that the binding specificities of the two preparations were nearly identical, and that CHAPS treatment had not altered the structure of the protein. Overall, solubilization improved displacement potency of the peptides tested by an average of half a log unit (threefold). Identification of FMRFamide-like peptides in squid optic lobe The demonstration of FMRFamide receptors in squid optic lobe suggests that FMRFamide itself should be de- tectable in this tissue. An acid extract of squid optic lobes was subjected to reverse-phase HPLC, and the fractionated eluant was analyzed both by radioimmunoassay (RIA) and by the radioreceptor assay described above. Some of the fractions were immunoreactive in the RIA with [I25I]- daYFnLRFa and anti-YGGFMRFamide antiserum S253 (Price, 1983). Most of the FMRFamide-immunoreactivity eluted in the positions of authentic FMRFamide and FLRFa (Fig. 14A). Moreover, the same HPLC fractions of the extract displaced [':5I]-daYFnLRFa from binding sites in squid optic lobe membranes: thus, the receptor- reactivity coeluted with the immunoreactivity in the po- sitions of FMRFamide and FLRFa (Fig. 14B). The results of both assays were in close agreement that the amount of FMRFamide in the tissue ( nmole/g wet weight) was about 13-to 14-fold that of FLRFa ( nmole/ g). An acetone extract of squid optic lobes was also sub- jected to reverse-phase HPLC on a C|g column, and the fractions were assayed w
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
