C-terminal bombesin sequence requirements for binding and effects on protein synthesis in Swiss 3T3 cells.
1. Synthetic peptides corresponding to the five, seven, nine and eleven C-terminal amino acids of the tetradecapeptide bombesin as well as bombesin itself and gastrin-releasing peptide have been evaluated in Swiss 3T3 cells in order to define the minimal peptide length needed for biological responsiveness. 2. Gastrin-releasing peptide, bombesin, the undecapeptide and nonapeptide had nearly equipotent abilities to compete for binding of labelled gastrin-releasing peptide to the cell receptors and showed half-maximal competition at 5-10 nM. The heptapeptide and pentapeptide were ineffective. 3. Cross-linking experiments demonstrated specific binding of gastrin-releasing peptide to a 100 kDa receptor subunit. 4. Total cell protein synthesis was stimulated equally by the nonapeptide and longer peptides with a half-maximal effect at 0.5 nM, while a more than 1000-fold higher concentration of the heptapeptide was required to produce a similar response. Comparable results were found when insulin was also present. 5. Neither an inhibition of protein breakdown nor a stimulation of DNA labelling could be demonstrated by bombesin or gastrin-releasing peptide. 6. We conclude that a C-terminal peptide ligand comprising more than seven but no more than nine amino acids is required to achieve high-affinity binding and receptor-mediated responses via the bombesin receptor.
Department of Biochemistry, University of Adelaide, South Australia.
S E
SE
Gargosky
J C
JC
Wallace
F M
FM
Upton
F J
FJ
Ballard
D000595:Amino Acid Sequence; D001665:Binding Sites; D001839:Bombesin / Q000494:pharmacology*; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D019886:Gastrin-Releasing Peptide; D006133:Growth Substances / Q000494:pharmacology; D008024:Ligands; D010455:Peptides / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis; D013936:Thymidine / Q000378:metabolism
D006133:Growth Substances; D008024:Ligands; D010455:Peptides; D019886:Gastrin-Releasing Peptide; D001839:Bombesin; D013936:Thymidine