Backbone dynamics of the regulatory domain of calcium vector protein, studied by 15N relaxation at four fields, reveals unique mobility characteristics of the intermotif linker
| Autor: | Isabelle Théret, Joël Mispelter, Jos A. Cox, Constantin T. Craescu |
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| Rok vydání: | 2008 |
| Předmět: |
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Movement Muscle Proteins Biochemistry Article Protein Structure Secondary Magnetics chemistry.chemical_compound Ion binding Chordata Nonvertebrate Calcium-binding protein Amide Animals Binding site Nuclear Magnetic Resonance Biomolecular Molecular Biology Binding Sites Nitrogen Isotopes Chemistry Protein dynamics Calcium-Binding Proteins Relaxation (NMR) Protein Structure Tertiary Microsecond Crystallography Calcium Linker |
| Zdroj: | Protein Science. 10:1393-1402 |
| ISSN: | 0961-8368 |
| DOI: | 10.1110/ps.190101 |
| Popis: | CaVP is a calcium-binding protein from amphioxus. It has a modular composition with two domains, but only the two EF-hand motifs localized in the C-terminal domain are functional. We recently determined the solution structure of this regulatory half (C-CaVP) in the Ca2+-saturated form and characterized the stepwise ion binding. This paper reports the 15N nuclear relaxation rates of the Ca2+-saturated C-CaVP, measured at four different NMR fields (9.39, 11.74, 14.1, and 18.7 T), which were used to map the spectral density function for the majority of the amide HN-N vectors. Fitting the spectral density values at eight frequencies by a model-free approach, we obtained the microdynamic parameters characterizing the global and internal movements of the polypeptide backbone. The two EF-hand motifs, including the ion binding loops, behave like compact structural units with restricted mobility as reflected in the quite uniform order parameter and short internal correlation time (< 20 nsec). Comparative analysis of the two Ca2+ binding sites shows that site III, having a larger affinity for the metal ion, is generally more rigid, and the amide vector in the second residue of each loop is significantly less restricted. The linker fragment is animated simultaneously by a larger amplitude fast motion and a slow conformational exchange on a microsecond to millisecond time scale. The backbone dynamics of C-CaVP characterized here is discussed in relation with other well-characterized Ca2+-binding proteins. Supplemental material: See www.proteinscience.org |
| Databáze: | OpenAIRE |
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