Narrowing the conformational space sampled by two-domain proteins with paramagnetic probes in both domains

• Published in: Journal of biomolecular NMR Vol. 51; no. 3; pp. 253 - 263
• Main Authors: Dasgupta, Soumyasri, Hu, Xiaoyu, Keizers, Peter H. J., Liu, Wei-Min, Luchinat, Claudio, Nagulapalli, Malini, Overhand, Mark, Parigi, Giacomo, Sgheri, Luca, Ubbink, Marcellus
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-11-2011; Springer Nature B.V
• Subjects: Binding Sites; Biochemistry; Biological and Medical Physics; Biophysics; Calcium; Calcium - chemistry; Calmodulin - chemistry; Calmodulin - metabolism; Electron Spin Resonance Spectroscopy; Lanthanoid Series Elements; Nuclear Magnetic Resonance, Biomolecular - methods; Physics; Physics and Astronomy; Protein Structure, Tertiary; Spectroscopy/Spectrometry; Conformational heterogeneity; Maximum occurrence; Paramagnetic tag; Paramagnetic proteins; Maximum allowed probability; Calmodulin
• ISSN: 0925-2738; 1573-5001
• DOI: 10.1007/s10858-011-9532-2

Calmodulin is a two-domain protein which in solution can adopt a variety of conformations upon reorientation of its domains. The maximum occurrence (MO) of a set of calmodulin conformations that are representative of the overall conformational space possibly sampled by the protein, has been calculated from the paramagnetism-based restraints. These restraints were measured after inclusion of a lanthanide binding tag in the C-terminal domain to supplement the data obtained by substitution of three paramagnetic lanthanide ions to the calcium ion in the second calcium binding loop of the N-terminal domain. The analysis shows that the availability of paramagnetic restraints arising from metal ions placed on both domains, reduces the MO of the conformations to different extents, thereby helping to identify those conformations that can be mostly sampled by the protein.