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2 results on '"G. Ansanelli"'

1. Bicyclic peptides as models of calcium binding sites: synthesis and conformation of a homodetic undecapeptide.

Author

Oliva R, Falcigno L, D'Auria G, Saviano M, Paolillo L, Ansanelli G, and Zanotti G

Subjects
Amino Acid Sequence, Binding Sites, Circular Dichroism, Indicators and Reagents, Models, Molecular, Nuclear Magnetic Resonance, Biomolecular, Oligopeptides chemical synthesis, Peptides, Cyclic chemical synthesis, Protein Conformation, Calcium metabolism, Calmodulin chemistry, Oligopeptides chemistry, Peptides, Cyclic chemistry
Abstract

A bicyclic undecapeptide of sequence cyclo-(Ala(1)-Pro(2)-Asp(3)-Glu(4)-Lys(5)-Ala(6)-Pro(7)-Asp(8)-Ser(9) -Glu(10))-cyclo-(10gamma --> 5varepsilon)-Gly(11), designed to mimic the calcium coordination site I of Calmodulin, has been synthesized and its conformation and calcium binding properties have been investigated by means of CD and nmr spectroscopy. The nmr analysis of the free peptide, carried out in DMSO and in TFE/H(2)O at different pH values, shows the presence in solution of one stable conformer, exhibiting trans configuration around both Proline residues. The nmr results in both solvents suggest for the molecule a rectangular shape constituted by two antiparallel beta-strands connected by two beta-turns. Interproton distances, evaluated by NOE contacts, have been used to obtain feasible models by means of Restrained Molecular Dynamic (RMD). The average models from RMD calculations, for both solvents, exhibit good analogies with Calmodulin site I. The model system, when compared with the reference system (Asp(20)-Glu(31) segment in CaM), shows similar dimensions and an effective superimposition of the respective sequence segments Ala(1)-Glu(4) and Thr(28)-Glu(31). The remaining segments of the model peptide exhibit a bending that is intermediate between that of the free and Ca(2+)-coordinated site I. CD spectra, recorded in TFE solutions, point to a 1:1 stoichiometry for the Ca(2+)-peptide complex, with an association constant of at least 1 x 10(5) M(-1)., (Copyright 2000 John Wiley & Sons, Inc.)

Published
2000
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2. Bicyclic peptides as models of calcium binding sites: synthesis and conformation of a homodetic undecapeptide

Author

Michele Saviano, Giancarlo Zanotti, Lucia Falcigno, Gabriella D'Auria, G. Ansanelli, Livio Paolillo, Romina Oliva, R., Oliva, Falcigno, Lucia, D'Auria, Gabriella, M., Saviano, L., Paolillo, G., Ansanelli, and G., Zanotti

Subjects
Models, Molecular, Circular dichroism, Calmodulin, Stereochemistry, Protein Conformation, Biophysics, Antiparallel (biochemistry), Biochemistry, Peptides, Cyclic, Biomaterials, Protein structure, Amino Acid Sequence, Conformational isomerism, Peptide sequence, Nuclear Magnetic Resonance, Biomolecular, Binding Sites, biology, Bicyclic molecule, Chemistry, Circular Dichroism, Organic Chemistry, General Medicine, Nuclear magnetic resonance spectroscopy, biology.protein, Calcium, Indicators and Reagents, Oligopeptides
Abstract

A bicyclic undecapeptide of sequence cyclo-(Ala(1)-Pro(2)-Asp(3)-Glu(4)-Lys(5)-Ala(6)-Pro(7)-Asp(8)-Ser(9) -Glu(10))-cyclo-(10gamma --> 5varepsilon)-Gly(11), designed to mimic the calcium coordination site I of Calmodulin, has been synthesized and its conformation and calcium binding properties have been investigated by means of CD and nmr spectroscopy. The nmr analysis of the free peptide, carried out in DMSO and in TFE/H(2)O at different pH values, shows the presence in solution of one stable conformer, exhibiting trans configuration around both Proline residues. The nmr results in both solvents suggest for the molecule a rectangular shape constituted by two antiparallel beta-strands connected by two beta-turns. Interproton distances, evaluated by NOE contacts, have been used to obtain feasible models by means of Restrained Molecular Dynamic (RMD). The average models from RMD calculations, for both solvents, exhibit good analogies with Calmodulin site I. The model system, when compared with the reference system (Asp(20)-Glu(31) segment in CaM), shows similar dimensions and an effective superimposition of the respective sequence segments Ala(1)-Glu(4) and Thr(28)-Glu(31). The remaining segments of the model peptide exhibit a bending that is intermediate between that of the free and Ca(2+)-coordinated site I. CD spectra, recorded in TFE solutions, point to a 1:1 stoichiometry for the Ca(2+)-peptide complex, with an association constant of at least 1 x 10(5) M(-1).

Published
2000

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