Solution structure and adenylyl cyclase stimulating activities of C-terminal truncated human parathyroid hormone analogues.
Analogues of human parathyroid hormone (hPTH) truncated at the C-terminal end have been studied for adenylyl cyclase (AC) activity and for solution conformation by circular dichroism (CD) spectroscopy. Analogues of hPTH-(1-34)-NH2, containing the first 28-31 residues, had only a slightly diminished ability to stimulate AC in rat osteosarcoma (ROS) cells as compared to that of the parent analogue. CD data on hPTH-(16-34)-NH2 and C-terminal deletion mutants of hPTH-(1-34)-NH2 supported the presence of a partially stable alpha-helix over residues 17-28. A carboxyl-terminal mutant, hPTH-(1-30)-OH, showed both reduced helix and greatly reduced AC-stimulating activity as compared to the corresponding amide analogue. In contrast, both of these analogues, in the presence of palmitoyloleoylphosphatidylserine (POPS) vesicles, showed an equal stabilization of alpha-helix. All other analogues showed at least some enhancement of alpha-helix in the presence of POPS. However, both in neutral, aqueous buffer and in POPS, the relative amount of alpha-helix decreased greatly as the peptide was shortened below the 1-28 sequence. These data provide additional support for an amphiphilic alpha-helix over residues 21-28 being the conformation for receptor binding of hPTH for stimulation of AC activity. Modeling human parathyroid hormone-related peptide as an alpha-helix over this same region, and comparison to hPTH, suggests that both may bind via the hydrophobic face to the receptor.
Neugebauer
W
W
Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
Barbier
J R
JR
Sung
W L
WL
Whitfield
J F
JF
Willick
G E
GE
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002942:Circular Dichroism; D004789:Enzyme Activation; D006801:Humans; D010281:Parathyroid Hormone / Q000737:chemistry / Q000502:physiology*; D010446:Peptide Fragments / Q000737:chemistry / Q000502:physiology; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D051381:Rats; D012996:Solutions; D014407:Tumor Cells, Cultured
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D012996:Solutions; D000262:Adenylyl Cyclases