Evidence for beta-turn structure in model peptides reproducing pro-ocytocin/neurophysin proteolytic processing site |
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Authors: | M Rholam P Cohen N Brakch L Paolillo A Scatturin C Di Bello |
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Affiliation: | Université Pierre et Marie Curie, URA 554 du CNRS, Paris, France. |
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Abstract: | The structural organization of small peptides reproducing the amino acid sequence of the common ocytocin/neurophysin precursor around the LysArg cleavage locus was investigated by a combination of spectroscopical techniques. In water both circular dichroism and [1H] NMR spectra indicated that these peptides adopted a random conformation. Evidence for folded structures was obtained when these compounds were placed in a membrane-like environment i.e. 40 mM SDS in phosphate buffer or trifluoroethanol. Whereas the CD spectra indicated the formation of various types of beta-turn in rapid equilibrium, measurements of NH temperature coefficients and Nuclear Overhauser Effects by 400 and 500 MHz NMR revealed the existence of contacts and of a folded conformation. These observations are discussed in relation with previous hypothesis made on the secondary structure organization of the proteolytic processing site of polypeptide hormone precursors. |
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