Folding behavior of a backbone-reversed protein: reversible polyproline type II to beta-sheet thermal transitions in retro-GroES multimers with GroES-like features.

Ahmed, Shubbir and Shukla, Anshuman and Guptasarma, Purnananda (2008) Folding behavior of a backbone-reversed protein: reversible polyproline type II to beta-sheet thermal transitions in retro-GroES multimers with GroES-like features. Biochimica et biophysica acta, 1784 (6). pp. 916-23. ISSN 0006-3002

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Abstract

The structural consequences of the reversal of polypeptide backbone direction (retro modification) remain insufficiently explored. Here, we describe the behavior of an engineered, backbone-reversed form of the 97 residues-long GroES co-chaperonin of Escherichia coli. FTIR and far-UV CD spectroscopy suggest that retro-GroES adopts a mixed polyproline type II (PPII)-beta-strand structure with a beta(II) type CD spectrum similar to that of GroES. Gel-filtration chromatography reveals that the protein adopts trimeric and/or pentameric quaternary structures, with solubility retained up to concentrations of 5.0-5.5 mg/ml in aqueous solutions. Mutations inserting a single tryptophan residue as a spectroscopic probe at three different sites cause no perturbation in the protein's CD spectral characteristics, or in its quaternary structural status. The protein is cooperatively dissociated, and non-cooperatively unfolded, by both guanidine hydrochloride and urea. Intriguingly, unlike with GroES, retro-GroES is not unfolded by heat. Instead, there is a reversible structural transition involving conversion of PPII structure to beta sheet structure, upon heating, with no attendant aggregation even at 90 degrees C. Retro-GroES does not bind GroEL. In summary, some structure-forming characteristics of GroES appear to be conserved through the backbone reversal process, although the differential conformational behavior upon heating also indicates differences.

Item Type:	Article
Additional Information:	Copyright of this article belongs to Elsevier Science
Uncontrolled Keywords:	Retro-protein; Protein folding; Protein engineering; Beta strand; Polyproline type II structure
Subjects:	Q Science > QH Natural history > QH301 Biology QH301 Biology
Depositing User:	Dr. K.P.S.Sengar
Date Deposited:	30 Nov 2011 09:59
Last Modified:	30 Nov 2011 11:25
URI:	http://crdd.osdd.net/open/id/eprint/612

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