Structure-activity relationships of FMRF-NH2 peptides demonstrate A role for the conserved C terminus and unique N-terminal extension in modulating cardiac contractility.
FMRF-NH2 peptides which contain a conserved, identical C-terminal tetrapeptide but unique N terminus modulate cardiac contractility; yet, little is known about the mechanisms involved in signaling. Here, the structure-activity relationships (SARs) of the Drosophila melanogaster FMRF-NH2 peptides, PDNFMRF-NH2, SDNFMRF-NH2, DPKQDFMRF-NH2, SPKQDFMRF-NH2, and TPAEDFMRF-NH2, which bind FMRFa-R, were investigated. The hypothesis tested was the C-terminal tetrapeptide FMRF-NH2, particularly F1, makes extensive, strong ligand-receptor contacts, yet the unique N terminus influences docking and activity. To test this hypothesis, docking, binding, and bioactivity of the C-terminal tetrapeptide and analogs, and the FMRF-NH2 peptides were compared. Results for FMRF-NH2 and analogs were consistent with the hypothesis; F1 made extensive, strong ligand-receptor contacts with FMRFa-R; Y → F (YMRF-NH2) retained binding, yet A → F (AMRF-NH2) did not. These findings reflected amino acid physicochemical properties; the bulky, aromatic residues F and Y formed strong pi-stacking and hydrophobic contacts to anchor the ligand, interactions which could not be maintained in diversity or number by the small, aliphatic A. The FMRF-NH2 peptides modulated heart rate in larva, pupa, and adult distinctly, representative of the contact sites influenced by their unique N-terminal structures. Based on physicochemical properties, the peptides each docked to FMRFa-R with one best pose, except FMRF-NH2 which docked with two equally favorable poses, consistent with the N terminus influencing docking to define specific ligand-receptor contacts. Furthermore, SDNAMRF-NH2 was designed and, despite lacking the aromatic properties of one F, it binds FMRFa-R and demonstrated a unique SAR, consistent with the N terminus influencing docking and conferring binding and activity; thus, supporting our hypothesis.
Department of Biological Chemistry, The University of Michigan Medical School, Ann Arbor, Michigan, United States of America ; Undergraduate Biochemistry Honors Research Program, Department of Chemistry, The University of Michigan, Ann Arbor, Michigan, United States of America.
Benjamin F
BF
Maynard
Chloe
C
Bass
Chris
C
Katanski
Kiran
K
Thakur
Beth
B
Manoogian
Megan
M
Leander
Ruthann
R
Nichols
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002766:Cholecystokinin / Q000737:chemistry / Q000378:metabolism; D004331:Drosophila melanogaster; D019835:FMRFamide / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008024:Ligands; D008297:Male; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D009200:Myocardial Contraction / Q000187:drug effects*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D043886:Receptor, Cholecystokinin A / Q000737:chemistry / Q000378:metabolism; D018010:Receptors, Invertebrate Peptide / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
C055209:FMRFamide receptor; D008024:Ligands; D010446:Peptide Fragments; D043886:Receptor, Cholecystokinin A; D018010:Receptors, Invertebrate Peptide; D019835:FMRFamide; D002766:Cholecystokinin