The effect of substitutions at position three on the binding and bioactivity of proctolin in locust hindgut and oviduct.
A number of proctolin analogs modified at position three were analyzed for their relative binding affinities and biological activity on locust hindgut and oviduct. A decrease in chain length at this position (from Leu, Ile to Val) or an increase in hydrophobicity alone (Glu) or combined with a decrease in chain length (Val, Ser, Thr and Asp) decreased bioactivity but not necessarily binding. (Ser3)-proctolin had a higher affinity than proctolin for both hindgut and oviduct membranes but was less biologically active than proctolin in both tissues. Several other analogs bound with a similar affinity to proctolin but were significantly less biologically active, particularly on locust oviduct. These results suggest that the position three leucine of proctolin is more important for bioactivity than for binding in both oviduct and hindgut. The data also suggest the presence of two proctolin receptor subtypes on oviduct but not on hindgut membranes. Position three proctolin analogs may be useful in more precisely distinguishing these subtypes.
King
L E
LE
Department of Biology, York University, North York, Ontario, Canada.
Sevala
V M
VM
Loughton
B G
BG
D000595:Amino Acid Sequence; D000818:Animals; D004064:Digestive System / Q000378:metabolism; D005260:Female; D006110:Grasshoppers; D008566:Membranes / Q000378:metabolism; D008969:Molecular Sequence Data; D009479:Neuropeptides; D018377:Neurotransmitter Agents / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D010057:Oviducts / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D012694:Serine / Q000737:chemistry; D013329:Structure-Activity Relationship
D009479:Neuropeptides; D018377:Neurotransmitter Agents; D009842:Oligopeptides; D010446:Peptide Fragments; D012694:Serine; C011536:proctolin