Synthesis, biological activity and conformational analysis of cyclic GRF analogs.
A novel cyclic GRF analog, cyclo(Asp8-Lys12)-[Asp8,Ala15]-GRF(1-29)-NH2, i.e. cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2, was synthesized by the solid phase procedure and found to retain significant biological activity. Solid phase cyclization of Asp8 to Lys12 proceeded rapidly (approximately 2 h) using the BOP reagent. Substitution of Ala2 with D-Ala2 and/or NH2-terminal replacement (desNH2-Tyr1 or N-MeTyr1) in the cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 system resulted in highly potent analogs that were also active in vivo. Conformational analysis (circular dichroism and molecular dynamics calculations based on NOE-derived distance constraints) demonstrated that cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 contains a long alpha-helical segment even in aqueous solution. A series of cyclo8,12 stereoisomers containing D-Asp8 and/or D-Lys12 were prepared and also found to be highly potent and to retain significant alpha-helical conformation. The high biological activity of cyclo8,12[N-MeTyr1,D-Ala2,Asp8,Ala15]-GRF(1-29)- NH2 may be explained on the basis of retention of a preferred bioactive conformation.
Felix
A M
AM
Physical Chemistry and Animal Science Research Dept., Roche Research Center, Hoffmann-La Roche Inc., Nutley, New Jersey.
Heimer
E P
EP
Wang
C T
CT
Lambros
T J
TJ
Fournier
A
A
Mowles
T F
TF
Maines
S
S
Campbell
R M
RM
Wegrzynski
B B
BB
Toome
V
V
D000818:Animals; D013007:Growth Hormone-Releasing Hormone / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000494:pharmacology; D007202:Indicators and Reagents; D007986:Luteinizing Hormone / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D011487:Protein Conformation; D051381:Rats; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D007202:Indicators and Reagents; D010456:Peptides, Cyclic; D007986:Luteinizing Hormone; D013007:Growth Hormone-Releasing Hormone