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Experimentally exploring the conformational space sampled by domain reorientation in calmodulin

Bertini, Ivano and Del Bianco, Cristina and Gelis, Ioannis and Katsaros, Nikolaus and Luchinat, Claudio and Parigi, Giacomo and Peana, Massimiliano Francesco and Provenzani, Alessandro and Zoroddu, Maria Antonietta (2004) Experimentally exploring the conformational space sampled by domain reorientation in calmodulin. Proceedings of The National Academy of Sciences, Vol. 101 (18), p. 6841-6846. eISSN 1091-6490. Article.

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DOI: 10.1073/pnas.0308641101

Abstract

The conformational space sampled by the two-domain protein calmodulin has been explored by an approach based on four sets of NMR observables obtained on Tb3+ and Tm3+substituted proteins. The observables are the pseudocontact shifts and residual dipolar couplings of the C-terminal domain when lanthanide substitution is at the N-terminal domain. Each set of observables provides independent information on the conformations experienced by the molecule. It is found that not all sterically allowed conformations are equally populated. Taking the N-terminal domain as the reference, the C-terminal domain preferentially resides in a region of space inscribed in a wide elliptical cone. The axis of the cone is tilted by ≈30° with respect to the direction of the N-terminal part of the interdomain helix, which is known to have a flexible central part in solution. The C-terminal domain also undergoes rotation about the axis defined by the C-terminal part of the interdomain helix. Neither the extended helix conformation initially observed in the solid state for free calcium calmodulin nor the closed conformation(s) adopted by calcium calmodulin either alone or in its adduct(s) with target peptide(s) is among the most preferred ones. These findings are unique, both in terms of structural information obtained on a biomolecule that samples multiple conformations and in terms of the approach developed to achieve the results. The same approach is in principle applicable to other multidomain proteins, as well as to multiple interaction modes between two macromolecular partners.

Item Type:Article
ID Code:1145
Status:Published
Refereed:Yes
Uncontrolled Keywords:Calmodulin (CaM), EF-hand proteins, helix conformation, N-terminal domain, C-terminal domain
Subjects:Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
Publisher:The National Academy of Sciences of the USA
eISSN:1091-6490
Publisher Policy:Depositato per gentile concessione dell'Editore. È vietato duplicare e postare il PDF. E' consentito l'uso a solo scopo di studio e di ricerca.
Deposited On:18 Aug 2009 10:04

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