Functional mode of NtHSP17.6, a cytosolic small heat-shock protein fromNicotiana tabacum |
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Authors: | Hae-jeong Yoon Keun Pill Kim Soo Min Park Choo Bong Hong |
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Affiliation: | (1) Institute of Molecular Biology and Genetics, Seoul National University, 151-742 Seoul, Korea;(2) Division of Biological Sciences, University of California, 95616 Davis, CA, USA |
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Abstract: | Small heat-shock proteins (sHsps) are ubiquitous stress proteins with molecular chaperone activity. They share characteristic homology with the α-crystallin protein of the mammalian eye lens as well as being ATP-independent in their chaperone activity. We isolated a clone for a cytosolic class I sHsp,NtHSP17.6, fromNicotiana tabacum, and analyzed its functional mode for such activity. Following its transformation intoEscherichia coli and its over-expression, NtHSPI 7.6 was purified and examinedin vitro. This purified NtHSPI 7.6 exhibited typical chaperone activity in a light-scattering test. It was enable to protect a model substrate, firefly luciferase, from heat-induced aggregation. Non-denaturing PAGE showed that NtHSP17.6 formed a dodecamer in its native conformation, and was bound to its substrate under heat stress. A labeling test with bis-ANS indicated that this binding might be linked to newly exposed hydrophobic sites of the NtHSPI 7.6 complexes during heat shock. Based on these data, we suggest that NtHSP17.6 is a molecular chaperone that functions as a dodecamer in a heat-induced manner. |
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Keywords: | in vitro activity luciferase (Luc) molecular chaperone small heat-shock protein (sHsp) |
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