Metal-controlled Interdomain Cooperativity in Parvalbumins
Thermodynamics, Cooperativity, Thermodynamic Domain, Structural Domain, Ef-hand, Protein Unfolding, Protein Denaturation, Intermediate, Metal Binding, Protein Cavities, Protein Intrinsic Disorder, Hyperthermophile, Allergen
Digital Object Identifier (DOI)
Conformational behavior of five homologous proteins, parvalbumins (PAs) from northern pike (α and β isoforms), Baltic cod, and rat (α and β isoforms), was studied by scanning calorimetry, circular dichroism, and bis-ANS fluorescence. The mechanism of the temperature-induced denaturation of these proteins depends dramatically on both the peculiarities of their amino acid sequences and on their interaction with metal ions. For example, the pike α-PA melting can be described by two successive two-state transitions with mid-temperatures of 90 and 120 °C, suggesting the presence of two thermodynamic domains. The intermediate state populated at the end of the first transition was shown to bind Ca2+ ions, and was characterized by the largely preserved secondary structure and increased solvent exposure of hydrophobic groups. Mg2+- and Na+-loaded forms of pike α-PA demonstrated a single two-state transition. Therefore, the mechanism of the PA thermal denaturation is controlled by metal binding. It ranged from the absence of detectable first-order transition (apo-form of pike PA), to the two-state transition (e.g., Mg2+- and Na+-loaded forms of pike α-PA), to the more complex mechanisms (Ca2+-loaded PAs) involving at least one partially folded intermediate. Analysis of isolated cavities in the protein structures revealed that the interface between the CD and EF subdomains of Ca2+-loaded pike α-PA is much more loosely packed compared with PAs manifesting single heat-sorption peak. The impairment of interactions between CD and EF subdomains may cause a loss of structural cooperativity and appearance of two separate thermodynamic domains. One more peculiar feature of pike α-PA is that depending on its interactions with metal ions, it can be an intrinsically disordered protein (apo-form), an ordered protein of mesophilic (Na+-bound state), thermophilic (Mg2+-form), or even of the hyperthermophilic origin (Ca2+-form).
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Citation / Publisher Attribution
Cell Calcium, v. 46, issue 3, p. 163-175
Scholar Commons Citation
Permyakov, Sergei E.; Bakunts, Anush G.; Permyakova, Maria E.; Denesyuk, Alexander I.; Uversky, Vladimir N.; and Permyakov, Eugene A., "Metal-controlled Interdomain Cooperativity in Parvalbumins" (2009). Molecular Medicine Faculty Publications. 563.