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Proline inhibits aggregation during protein refolding

Published online by Cambridge University Press:  01 February 2000

DHARMARAJ SAMUEL
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
THALLAMPURANAM KRISHNASWAMY S. KUMAR
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan Institute of Chemistry, Academia Sinica, Taipei, Taiwan
GOPAL GANESH
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
GURUNATHAN JAYARAMAN
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan Present address: Institute of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan.
PEY-WEN YANG
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
MEI-MING CHANG
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
VISHWA DEO TRIVEDI
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan Institute of Chemistry, Academia Sinica, Taipei, Taiwan
SUE-LEIN WANG
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
KUO-CHU HWANG
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
DING-KWO CHANG
Affiliation:
Institute of Chemistry, Academia Sinica, Taipei, Taiwan
CHIN YU
Affiliation:
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
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Abstract

The in vitro refolding of hen egg-white lysozyme is studied in the presence of various osmolytes. Proline is found to prevent aggregation during protein refolding. However, other osmolytes used in this study fail to exhibit a similar property. Experimental evidence suggests that proline inhibits protein aggregation by binding to folding intermediate(s) and trapping the folding intermediate(s) into enzymatically inactive, “aggregation-insensitive” state(s). However, elimination of proline from the refolded protein mixture results in significant recovery of the bacteriolytic activity. At higher concentrations (>1.5 M), proline is shown to form loose, higher-order molecular aggregate(s). The supramolecular assembly of proline is found to possess an amphipathic character. Formation of higher-order aggregates is believed to be crucial for proline to function as a protein folding aid. In addition to its role in osmoregulation under water stress conditions, the results of this study hint at the possibility of proline behaving as a protein folding chaperone.

Type
Research Article
Copyright
© 2000 The Protein Society

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