NMR conformational studies on a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor

The results of a conformational study by nuclear magnetic spectroscopy and computational methods on a series of point-mutated synthetic peptides, containing 14 amino acid residues and mimicking the region containing the Arg-Lys dibasic cleavage site of pro-somatostatin, have confirmed the possible role of a well defined secondary structure in the recognition phenomenon by processing enzymes. The importance of the residues located near the Arg-Lys dibasic site in the C-terminal region of the pro-hormone for the cleavage of the precursor into somatostatin-14 has been confirmed. The present structural analysis indicates the occurrence of two beta-turns in the 4-7 and 11-14 regions, flanking the cleavage site, for all the peptides recognized as substrates by the processing enzyme. Interestingly, in the point-mutated analogue not processed by the enzyme and containing the replacement of proline by alanine in position 5 the first -turn is displaced by one residue and involves the Ala5-Arg8 segment. This observation may explain the lack of recognition by the maturation enzyme.

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A conformational study in solution of pro-somatostatin fragments by NMR and computational methods

Falcigno

Fraternali

Manduca

et al. 1998

J. Peptide Sci.

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New Fourier transform infrared based computational method for peptide secondary structure determination. I. Description of method

Simonetti

Bello

2001

Biopolymers

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Fourier transform infrared (FTIR) experiments in dimethylsulfoxide, a solvent incapable of H donation, demonstrate that H --> D isotopic replacement on the amide side of peptide bonds involves modifications of both the position and intensity of the amide I band. The effect of the isotopic substitution is particularly significant in the 1710-1670 and 1670-1650 cm(-1) regions, which are generally associated with beta-turns and alpha-helices. This behavior, attributed to the existence of intramolecular H-bonds in the polypeptide chain, is directly correlated to the presence of different secondary structures. Utilizing the effects induced by isotopic substitution, a method for the quantitative determination of the percentage of intramolecular H-bonds and the correlated secondary structures is proposed. The method consists of three principal steps: resolution of the fine structure of the amide I band with the determination of the number and position of the different components; reconstruction of the experimentally measured amide I band as a combination of Gaussian and Lorentzian functions, centered on the wave numbers set by band-narrowing methods, through a curve-fitting program; and quantitative determination of the population of the H-bonded carbonyls and the correlated secondary structures by comparison of the integrated intensities pertaining to the components with homologous wave numbers before and after isotopic exchange. The method is tested on a synthetic fragment of proocytocin that was previously analyzed by NMR techniques using the same solvent systems.

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New Fourier transform infrared based computational method for peptide secondary structure determination. II. Application to study of peptide fragments reproducing processing site of ocytocin–neurophysin precursor

Simonetti

Bello

2001

Biopolymers

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A new method for the quantitative determination of the percentage of intramolecular H-bonds, based on Fourier transform infrared techniques, is applied to the conformational analysis of a series of synthetic peptides spanning the processing site of the ocytocin and neurophysin precursor. Even though the method uses traditional tools such as Fourier self-deconvolution, the Nth derivative, and curve-fitting procedures for the analysis of the spectra, the assignment of the absorptions due to peptide groups participating into secondary structures is based on the direct observation and quantification of the isotopic effect induced on the groups participating in intramolecular H-bonds in the presence of organic solvents. This permits the quantification of the different populations of molecules containing intramolecular H-bonds involved in beta-turns and alpha-helices. The results are consistent with those previously obtained by NMR techniques in the same solvent systems.

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NMR conformational studies on a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor

Cited by 10 publications

References 43 publications

A conformational study in solution of pro-somatostatin fragments by NMR and computational methods

A conformational study in solution of pro-somatostatin fragments by NMR and computational methods

New Fourier transform infrared based computational method for peptide secondary structure determination. I. Description of method

New Fourier transform infrared based computational method for peptide secondary structure determination. II. Application to study of peptide fragments reproducing processing site of ocytocin–neurophysin precursor

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