Paramagnetism-Based Refinement Strategy for the Solution Structure of Human α-Parvalbumin

• Published in: Biochemistry (Easton) 2004-05, Vol.43 (18), p.5562-5573
• Main Authors: Baig, Irfan, Bertini, Ivano, Del Bianco, Cristina, Gupta, Yogesh Kumar, Lee, Yong-Min, Luchinat, Claudio, Quattrone, Alessandro
• Format: Article
• Language: English
• Subjects: Amides - chemistry; Animals; Anisotropy; Calcium-Binding Proteins - chemistry; Carbon Isotopes; Crystallography, X-Ray; Dysprosium - chemistry; EF Hand Motifs; Humans; Models, Molecular; Nitrogen Isotopes; Nuclear Magnetic Resonance, Biomolecular - methods; Parvalbumins - chemistry; Protein Conformation; Protein Isoforms - chemistry; Protons; Rats; Solutions
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi035879k

In the frame of a research aimed at the detailed structural characterization of human calcium-binding proteins of the EF-hand family, the solution structure of human α-parvalbumin has been solved by NMR and refined with the help of substitution of the Ca2+ ion in the EF site with the paramagnetic Dy3+ ion. A simple 1H−15N HSQC spectrum allowed the NH assignments based on the properties of Dy3+. This allowed us to exploit pseudocontact shifts and residual dipolar couplings for solution structure refinement. The backbone and heavy atom RMSD are 0.55 ± 0.08 and 1.02 ± 0.08 Å, respectively, and decrease to 0.39 ± 0.05 and 0.90 ± 0.06 Å upon refinement with paramagnetism-based restraints. The RMSD for the metal itself in the EF site in the refined structure is 0.26 ± 0.12 Å. Backbone NH R 1, R 2, and NOE measured at two temperatures show the protein to be relatively rigid. The NH orientations are well determined by the paramagnetism-based restraints. This allows us to detect small but significant local structural differences with the orthologue protein from rat, whose X-ray structure is available at 2.0 Å resolution. All differences are related to local changes in the amino acidic composition.