Radioligand binding properties of VV-hemorphin 7, an atypical opioid peptide.
Receptor binding properties of the hemoglobin-derived nonapeptide VV-hemorphin 7 (Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe-OH) were studied using both the unlabelled form and tritium-labelled derivative of the peptide. In binding studies using selective opioid radioligands, VV-hemorphin 7 exhibited a rank order of potency of mu > kappa >> delta. VV-hemorphin 7 was tritiated resulting in a compound with 1.03 TBq/mmol (27.8 Ci/mmol) specific radioactivity. The maximal number of binding sites was found to be 66.5 pmol/mg protein with an affinity of 82.1 nM in rat brain membranes. In competition studies, marked similarity was observed to the binding profile of the naturally occurring opioid heptapeptide Met-enkephalin-Arg-Phe (MERF) and its analogues to their naloxone-insensitive binding site. The common -Arg-Phe sequence at the carboxyl terminal end, which is similar to those of other endogenous peptides (-Arg-Phe-NH(2) in neuropeptide FF and FMRF-NH(2)) brings attention to the C-terminal end of the molecule and points to the possible existence of a common nonopioid binding site in mammals.
Szikra
J
J
Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, Szeged, H-6701, Hungary
Benyhe
S
S
Orosz
G
G
Darula
Z
Z
Piot
J M
JM
Fruitier
I
I
Monory
K
K
Hanoune
J
J
Borsodi
A
A
D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011869:Radioligand Assay; D051381:Rats; D014316:Tritium
D006454:Hemoglobins; D010446:Peptide Fragments; D014316:Tritium; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C094394:VV-hemorphin-7