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Reversible formation of on-pathway macroscopic aggregates during the folding of maltose binding protein

Ganesh, C and Zaidi, Faisal N and Udgaonkar, Jayant B and Varadarajan, Raghavan (2001) Reversible formation of on-pathway macroscopic aggregates during the folding of maltose binding protein. In: Protein Science, 10 (8). 1635 -1644.

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Maltose binding protein (MBP) is widely used as a model for protein folding and export studies. We show here that macroscopic aggregates form transiently during the refolding of MBP at micromolar protein concentrations. Disaggregation occurs spontaneously without any aid, and the refolded material has structure and activity identical to those of the native, nondenatured protein. A considerable fraction of protein undergoing folding partitions into the aggregate phase and can be manually separated from the soluble phase by centrifugation. The separated MBP precipitate can be resolubilized and yields active, refolded protein. This demonstrates that both the soluble and aggregate phases contribute to the final yield of refolded protein. SecB, the cognate Escherichia coli cytosolic chaperone in vivo for MBP, reduces but does not entirely prevent aggregation, whereas GroEL and a variety of other control proteins have no effect. Kinetic studies using a variety of spectroscopic probes show that aggregation occurs through a collapsed intermediate with some secondary structure. The aggregate formed during refolding can convert directly to a near native state without going through the unfolded state. Further, optical and electron microscopic studies indicate that the MBP precipitate is not an amyloid.

Item Type: Journal Article
Publication: Protein Science
Publisher: The Protein Society
Additional Information: Copyright of this article belongs to The Protein Society.
Keywords: Aggregation;Intermediates;Folding;MBP
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 03 Oct 2007
Last Modified: 04 Jan 2013 06:03
URI: http://eprints.iisc.ac.in/id/eprint/12054

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