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The prolactin releasing peptide (PrRP) is involved in regulating food intake and body weight homeostasis, but molecular details on the activation of the PrRP receptor remain unclear. C-terminal segments of PrRP with 20 (PrRP20) and 13 (PrRP8-20) amino acids, respectively, have been suggested to be fully active. The data presented herein indicate this is true for the wildtype receptor only; a 5-10-fold loss of activity was found for PrRP8-20 compared to PrRP20 at two extracellular loop mutants of the receptor. To gain insight into the secondary structure of PrRP, we used CD spectroscopy performed in TFE and SDS. Additionally, previously reported NMR data, combined with ROSETTANMR, were employed to determine the structure of amidated PrRP20. The structural ensemble agrees with the spectroscopic data for the full-length peptide, which exists in an equilibrium between α- and 3(10)-helix. We demonstrate that PrRP8-20's reduced propensity to form an α-helix correlates with its reduced biological activity on mutant receptors. Further, distinct amino acid replacements in PrRP significantly decrease affinity and activity but have no influence on the secondary structure of the peptide. We conclude that formation of a primarily α-helical C-terminal region of PrRP is critical for receptor activation.
Copyright © 2012 Wiley Periodicals, Inc.
We have produced and characterized a murine monoclonal antibody that recognizes DNA modified with N-acetoxy-2-acetylaminofluorene. The effectiveness of competitive binding inhibitors in an ELISA indicates that this antibody binds most strongly to N-(guanin-8-yl)-2-acetylaminofluorene. It also binds to N-(guanin-8-yl)-2-aminofluorene, albeit some 20-fold less avidly. Thus the monoclonal antibody displays specificity generally similar to the polyclonal antisera elicited by other laboratories but having the advantage of stable and precisely defined specificities. We employed a biotin-streptavidin ELISA to demonstrate that the antibody can detect less than 10 fmol of N-(guanin-8-yl)-2-acetylaminofluorene. N-(guanin-8-yl)-2-acetylaminofluorene is a more effective competitive binding inhibitor of the antibody than is N-(2'-deoxyguanosin-8-yl)-2-acetylaminofluorene or calf thymus DNA modified with N-acetoxy-2-acetylaminofluorene. Thus the antibody should be most useful in quantifying the persistence of N-acetoxy-2-acetylaminofluorene adducts in DNA hydrolyzed with trifluoroacetic acid.