Small heat shock proteins prevent aggregation of citrate synthase and bind to the N-terminal region which is absent in thermostable forms of citrate synthase |
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Authors: | Emma Åhrman Niklas Gustavsson Claus Hultschig Wilbert C Boelens Cecilia Sundby Emanuelsson |
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Institution: | (1) Department of Biochemistry, Lund University, Lund, Sweden;(2) The Max Planck Institute for Molecular Genetics, Berlin, Germany;(3) Department of Biochemistry, Radboud University Nijmegen, Nijmegen, The Netherlands |
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Abstract: | Citrate synthase (CS) is often used in chaperone assays since this thermosensitive enzyme aggregates at moderately increased
temperatures. Small heat shock proteins (sHsps) are molecular chaperones specialized in preventing the aggregation of other
proteins, termed substrate proteins, under conditions of transient heat stress. To investigate the mechanism whereby sHsps
bind to and stabilize a substrate protein, we here used peptide array screening covering the sequence of porcine CS (P00889).
Strong binding of sHsps was detected to a peptide corresponding to the most N-terminal α-helix in CS (amino acids Leu13 to Gln27). The N-terminal α-helices in the CS dimer intertwine with the C-terminus in the other subunit and together form a stem-like
structure which is protruding from the CS dimer. This stem-like structure is absent in thermostable forms of CS from thermophilic
archaebacteria like Pyrococcus furiosus and Sulfolobus solfatacarium. These data therefore suggest that thermostabilization of thermosensitive CS by sHsps is achieved by stabilization of the
C- and N-terminae in the protruding thermosensitive softspot, which is absent in thermostable forms of the CS dimer. |
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Keywords: | Chaperones Heat stress Protein– protein interactions Protein stability Thermosensitivity |
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