In search for globally disordered apo-parvalbumins: Case of parvalbumin β-1 from coho salmon

• Published in: Cell calcium (Edinburgh) 2017-11, Vol.67, p.53-64
• Main Authors: Vologzhannikova, Alisa A., Khorn, Polina A., Kazakov, Alexei S., Ismailov, Ramis G., Sokolov, Andrei S., Uversky, Vladimir N., Permyakov, Eugene A., Permyakov, Sergei E.
• Format: Article
• Language: English
• Subjects: Animals; Apoproteins - chemistry; Apoproteins - genetics; Apoproteins - metabolism; Calcium - chemistry; Calcium - metabolism; Calcium-binding proteins; Calcium-Binding Proteins - chemistry; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cloning, Molecular; EF-hand; Escherichia coli - genetics; Escherichia coli - metabolism; Fish Proteins - chemistry; Fish Proteins - genetics; Fish Proteins - metabolism; Gene Expression; Genetic Vectors - chemistry; Genetic Vectors - metabolism; Intrinsically disordered proteins; Intrinsically Disordered Proteins - chemistry; Intrinsically Disordered Proteins - genetics; Intrinsically Disordered Proteins - metabolism; Molten globule state; Oncomodulin; Oncorhynchus kisutch - metabolism; Parvalbumin; Parvalbumins - chemistry; Parvalbumins - genetics; Parvalbumins - metabolism; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Folding; Protein Stability; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Thermodynamics
• ISSN: 0143-4160; 1532-1991
• DOI: 10.1016/j.ceca.2017.08.011

[Display omitted] •Parvalbumins (PAs) are calcium-binding proteins that are major fish allergens.•Allergenicity of PAs is favored by high structural stability of their calcium forms.•Conformational stability of apo-PAs affects metal affinity of these proteins.•A set of rules for prediction of apo-PA stability is elaborated.•It can be used in search for hypoallergenic PAs needed for immunotherapy of fish allergy. Parvalbumin (PA) is a classical EF-hand calcium-binding protein of muscle, neuronal, and other tissues, and a major fish allergen. Although certain apo-PAs lack tertiary structure, functional implications of that feature and its structural prerequisites remain unclear. In a search for unstable PAs, we probed conformational stability of parvalbumin β-1 from coho salmon (csPA), a cold water fish species, using circular dichroism, scanning calorimetry, hydrophobic probe fluorescence, limited proteolysis, chemical crosslinking and dynamic light scattering techniques. Apo-csPA is shown to be mainly monomeric protein with markedly disorganized secondary structure and lack of rigid tertiary structure. Examination of per-residue propensity for intrinsic disorder in the PA groups with either folded or unfolded apo-form using the average PONDR® VSL2P profiles revealed that the N-terminal region that includes α-helix A, AB-loop and N-terminal half of α-helix B is predicted to be less ordered in PAs with disordered apo-state. Application of the structural criteria developed for discrimination of disordered PAs indicate that the latter comprise about 16–19% of all PAs. We show that structural instability of apo-β-PA serves as a hallmark of elevated calcium affinity of the protein. Therefore, the successful predictions of unstable apo-PAs might facilitate search for PAs with maximal calcium affinity and possibly serving as calcium sensors.