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1 H‐nmr studies of the 20–31 fragment of calmodulin and of its cyclic analogue
Author(s) -
Motta Andrea,
Tancredi Teodorico,
Borin Gianfranco,
Marchiori Ferdinando,
Peggion Evaristo,
Temussi Pierandrea
Publication year - 1988
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360270507
Subject(s) - chemistry , calmodulin , titration , cyclic peptide , nuclear magnetic resonance spectroscopy , aqueous solution , stereochemistry , peptide , proton nmr , spectroscopy , equilibrium constant , crystallography , calcium , organic chemistry , biochemistry , physics , quantum mechanics
High‐resolution 1 H‐nmr spectroscopy at 500 MHz has been used to study the Ca 2+ binding domain I of bovine brain calmodulin in aqueous solution. All the resonances of the linear dodecapeptide Asp‐Lys‐Asp‐Gly‐Asn‐Gly‐Thr‐Ile‐Thr‐Thr‐Lys‐Glu and of its cyclic analogue, synthesized by classical solution methods, have been completely assigned using a combination of several one‐ and two‐dimensional nmr experiments, including the zero quantum correlation. Chemical shift values and 3 J CHNH coupling constants indicate that, on the nmr time scale, both peptides are flexible and assume multiple conformations in rapid equilibrium, with no relevant contribution of structured features. Addition of Ca 2+ causes only minor spectral changes in aqueous solution of both peptides, while larger effects are observed in more hydrophobic mixtures such as water/trifluoroethanol. The linear analogue shows nonspecific interactions, while only Asp 3 and Asn 5 are significantly perturbed in the cyclic peptide. This evidence, together with identical findings in La 3+ titration studies of the cyclic analogue in pure water, suggest that loop I of calmodulin is endowed with an intrinsic binding ability.