TY  - JOUR
ID  - open612
UR  - http://www.sciencedirect.com/science/article/pii/S1570963908000721
IS  - 6
A1  - Ahmed, Shubbir
A1  - Shukla, Anshuman
A1  - Guptasarma, Purnananda
N2  - 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.
VL  - 1784
TI  - Folding behavior of a backbone-reversed protein: reversible polyproline type II to beta-sheet thermal transitions in retro-GroES multimers with GroES-like features.
AV  - restricted
EP  - 23
N1  - Copyright of this article belongs to Elsevier Science
Y1  - 2008/06//
PB  - Elsevier Science
JF  - Biochimica et biophysica acta
KW  - Retro-protein; Protein folding; Protein engineering; Beta strand; Polyproline type II structure
SN  - 0006-3002
SP  - 916
ER  -