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Biologically potent analogues of salmon calcitonin which do not contain an N-terminal disulfide-bridged ring structure

Authors

  • Ronald C. ORLOWSKI,

    1. Armour Pharmaceutical Company, Kankakee, Illinois
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  • Richard M. EPAND,

    Corresponding author
    1. Department of Biochemistry, McMaster University, Health Sciences Centre, Hamilton, Ontario
      Correspondence to R. M. Epand, Department of Biochemistry, McMaster University, Health Sciences Centre, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5
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  • Alan R. STAFFORD

    1. Department of Biochemistry, McMaster University, Health Sciences Centre, Hamilton, Ontario
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Correspondence to R. M. Epand, Department of Biochemistry, McMaster University, Health Sciences Centre, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5

Abstract

The disulfide bridge formed between the cysteine residues at positions 1 and 7 of salmon calcitonin (sCT) is not required for biological activity. The analogues [Ala1,7]sCT, [AcmCys1,7]sCT and [AmcCys1,Ala7]sCT (AcmC =S-acetamido-methylcysteine) are linear sequences which retain full hypocalcemic activity in the intact rat and ability to activate adenylate cyclase of rat renal membranes. The secondary structure of these peptides in aqueous solution in the presence or absence of lipid is not greatly perturbed by the opening of the disulfide ring.

In contrast with salmon calcitonin, substitution of Cys by AcmCys in human calcitonin results in greatly reduced hypocalcemic activity but no loss in the ability of the peptide to activate renal adenylate cyclase. Thus in vitro activation of adenylate cyclase by human calcitonin analogues is not always correlated with in vivo hypocalcemic potency.

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