Conformational Requirements for Activity of Salmon Calcitonin*

Abstract

A series of deletion-substitution analogs of salmon calcitonin (SCT) have been prepared containing combinations of a glycine substitution in position 8 and deletions of serine-2 and tyrosine-22. Biological activity of the analogs with respect to native SCT were determined in the rat hypocalcemic assay and by studying stimulation of cAMP formation and competition for binding of 125I-labeled SCT in T47 D human breast cancer cells. It was found that each of the analogs retained full potency, irrespective of the means of assessment. It is suggested that conservation of the alpha-helical region of SCT, along with the overall tertiary structure, are more important for peptide potency than chain length per se.

Rational design, conformational studies and bioactivity of highly potent conformationally constrained calcitonin analogues

“…The design of such analogues will depend on understanding the structural and conformational requirements of hCt bioactivity, which have not yet been defined. In addition to the long proposed role of amphiphilic α helix formation, conformational flexibility, tertiary structure interactions, other, as yet unidentified, factors have been proposed to contribute to Ct bioactivity [9,11–13,16,20, 23,25,28,35,36].…”

“…In recent years, structure–activity relationships of Cts from various species have been studied extensively [3,9–19]. These studies demonstrated that a full‐length Ct sequence is necessary for bioactivity, while it was also suggested that a potential amphiphilic α‐helical region between residues 8 and 22 may be important.…”

Enhancing effect of chemically conjugated deoxycholic acid on permeability of calcitonin in Caco-2 cells

“…The biological activity of the modified sCT was determined by cell-based cAMP assay using T-47D cells, a human breast carcinoma cell line that endogenously expresses human CT receptors on the cell surface [Findlay et al, 1985]. T-47D cells were cultured at 371C in a 5% CO 2 humidified atmosphere in RPMI 1640 supplemented with 10% fetal calf serum containing 0.1 mM of insulin, 50 mg/mL streptomycin, and 50 U/mL penicillin.…”

Contribution of Conformationally Constrained Calcitonin (Ct) Analogs to the Understanding of the Structural and Conformational Requirements of Calcitonin Bioactivity and to the Design of Potent Agonists

“…Therefore, sCt has been preferred over hCt for therapeutic applications of bone disorder diseases. In addition, due to its high in vivo potency, the structural and conformational features of sCt have most extensively been studied and compared to those of hCt [20,21,41,42,[52][53][54][55][56][57][58][59][60][61][62][63][64][65][66]. Except for the disulfide bridge between Cys 1 and Cys 7 and the C-terminal prolinamide residue, common features of the Ct sequences from several species, including sCt and hCt, which are 50% homologeous to each other, are a highly conserved sequence stretch between residues 3-7 in the N-terminal loop and conserved amino acid residues in positions 1, 9, 28 and 32 ( Fig.…”

“…Of note, the results of the studies with these analogs also indicated that an ideal amphiphilic α-helix may not necessarily correlate with high Ct bioactivity. The role of the α-helix-forming propensity of Cts for bioactivity was further studied using a series of linear α-helical and/or non-α-helical Ct analogs [42,[53][54][55][56][57]71,72]. The amphiphilic α-helical structure of sCt was suggested to be important for peptide binding to the cell membrane [41,43,55].…”