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Correlation between Al3+-induced thermal stability and inhibition of fibrillation of N-terminal domain of the hydrogenase maturation factor

Authors

  • Nimesh M. Sutariya,

    1. Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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  • Shivcharan Prasad,

    1. Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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    • Shivcharan Prasad and Dipti A. Athavale contributed equally to this work.

  • Dipti A. Athavale,

    1. Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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    • Shivcharan Prasad and Dipti A. Athavale contributed equally to this work.

  • Rupen D. Bhavsar,

    1. Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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  • Ipsita Roy

    Corresponding author
    1. Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
    • Address for correspondence: Dr. Ipsita Roy, Ph.D., Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar, Punjab 160 062, India. Tel.:+ 91–172-229 2061; Fax:+ 91–172-221 4692; E-mail: ipsita@niper.ac.in.

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Abstract

Fibrillation can be induced in proteins by altering solvent conditions. Stabilization of the protofibrillar structure arrests formation of longer fibers. Thermal stability and fibrillation of N-terminal domain of the hydrogenase maturation factor (HypF-N) were studied in the presence of a series of metal ions. Only Al3+ was able to reverse the thermal denaturation of HypF-N upon heating. On being exposed to denaturing conditions, the native protein formed fibrillar structure under moderately denaturing conditions, whereas in the presence of Al3+, the protein was found to retain its native conformation. Under strongly denaturing conditions, only Al3+ was able to stabilize the protein in the fibrillar state. Spectrofluorimetric analysis revealed that Al3+ alone was able to stabilize the partially unfolded intermediate state of HypF-N. Based on the similarity in observations, we propose a link between reversal of thermal instability of HypF-N and its ability to form an intermediate structure in the presence of Al3+. Al3+ stabilizes the partially unfolded state in the N↔I↔U equilibrium so that upon heating, the three-dimensional structure of the protein is not lost completely. Kinetic analysis confirmed that Al3+ interacts with an early structure on the aggregation landscape and delays fibrillation. Under mildly denaturing state, HypF-N is able to recover its native conformation in the presence of Al3+ and under strongly denaturing conditions, the protein does not acquire a completely disordered structure. Instead, it forms an ordered β-sheet-rich structure. © 2013 BioFactors, 39(6):597–607, 2013

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