Characterization and Solubilization of the FMRFamide Receptor of Squid
The optic lobe of squid (Loligo pealei) contains FMRFamide receptors that can bind an iodinated FMRFamide analog: [125 I]-desaminoTyr-Phe-norLeu-Arg-Phe-amide ([125 I]-daYFnLRFa). Radioligand binding assays revealed that squid FMRFamide receptors are specific, saturable, high affinity sites ( K d=0....
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Published in | The Biological bulletin (Lancaster) Vol. 187; no. 2; pp. 185 - 199 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Marine Biological Laboratory
01.10.1994
University of Chicago Press |
Subjects | |
Online Access | Get full text |
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Summary: | The optic lobe of squid (Loligo pealei) contains FMRFamide receptors that can bind an iodinated FMRFamide analog: [125 I]-desaminoTyr-Phe-norLeu-Arg-Phe-amide ([125 I]-daYFnLRFa). Radioligand binding assays revealed that squid FMRFamide receptors are specific, saturable, high affinity sites ( K d=0.15 nM) densely concentrated in optic lobe membranes ( B max=237 fmole/ mg protein). The receptors appeared to be coupled to G s because guanine nucleotides inhibit receptor binding and the stimulation of adenylate cyclase by FMRFamide is GTP-dependent. Both the binding and cyclase data showed that FMRFamide, but not FMRF-OH, interacts at FMRFamide receptors; thus the C-terminal Arg-Phe-amide is critical for binding. The high binding affinity of FMRFamide (0.4 nM IC50) was specific for FMRFamide-like peptides. The structure-activity relations of many FMRFamide analogs were defined in detail and were nearly identical for both the membrane-bound and detergent-solubilized receptors. We also found that squid optic lobe contains FMRFamide-like reactivity as measured with both a radioimmunoassay and a radioreceptor assay. Moreover, we have sequenced a fragment of genomic DNA that encodes a FMRFamide precursor. Our findings in sum suggest that FMRFamide is a neurotransmitter in squid optic lobe, and that this tissue is a good source from which to purify FMRFamide receptors. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-3185 1939-8697 |
DOI: | 10.2307/1542241 |