International Journal of Peptide and Protein Reseach 1985-04-01

Conformational preferences and binding to neurophysins of oxytocin analogs with sarcosine or N-methylalanine in position 7.

Z Grzonka, P K Mishra, A A Bothner-By

Index: Int. J. Pept. Protein Res. 25(4) , 375-81, (1985)

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Abstract

The 600 MHz proton n.m.r. spectra of (sarcosyl7)-oxytocin and (N-methylalanyl7) oxytocin in 2H2O solution have been recorded and completely assigned. In each case the spectrum indicates the presence of two slowly interconverting conformers, which are the cis-trans isomers about the peptide bond between residues six and seven. The trans isomer is energetically favored in both cases. When neurophysin is added to a solution of (N-methylalanyl7) oxytocin or (sacrosyl7)-oxytocin at pH 3.0, the proportion of minor conformer remains constant, indicating that the cis and trans conformers are equally tightly bound to the protein.