1pv2
From Proteopedia
Native Form 2 E.coli Chaperone Hsp31
Structural highlights
Function[HCHA_ECOLI] Functions as a holding molecular chaperone (holdase) which stabilizes unfolding intermediates and rapidly releases them in an active form once stress has abated. Plays an important role in protecting cells from severe heat shock and starvation, as well as in acid resistance of stationary-phase cells. It uses temperature-induced exposure of structured hydrophobic domains to capture and stabilizes early unfolding and denatured protein intermediates under severe thermal stress. Catalyzes the conversion of methylglyoxal (MG) to D-lactate in a single glutathione (GSH)-independent step. It can also use phenylglyoxal as substrate. Glyoxalase activity protects cells against dicarbonyl stress. Displays an aminopeptidase activity that is specific against peptide substrates with alanine or basic amino acids (lysine, arginine) at N-terminus.[1] [2] [3] [4] [5] [6] [7] [8] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedHeat shock proteins and proteases play a crucial role in cell survival under conditions of environmental stress. The heat shock protein Hsp31, produced by gene hchA at elevated temperatures in Escherichia coli, is a homodimeric protein consisting of a large A domain and a smaller P domain connected by a linker. Two catalytic triads are present per dimer, with the Cys and His contributed by the A domain and an Asp by the P domain. A new crystal Form II confirms the dimer and catalytic triad arrangement seen in the earlier crystal Form I. In addition, several loops exhibit increased flexibility compared to the previous Hsp31 dimer structure. In particular, loops D2 and D3 are intriguing because their mobility leads to the exposure of a sizable hydrophobic patch made up by surface areas of both subunits near the dimer interface. The residues creating this hydrophobic surface are completely conserved in the Hsp31 family. At the same time, access to the catalytic triad is increased. These observations lead to the hypothesis for the functioning of Hsp31 wherein loops D2 and D3 play a key role: first, at elevated temperatures, by becoming mobile and uncovering a large hydrophobic area that helps in binding to client proteins, and second, by removing the client protein from the hydrophobic patch when the temperature decreases and the loops adopt their low-temperature positions at the Hsp31 surface. The proposed mode of action of flexible loops in the functioning of Hsp31 may be a general principle employed by other chaperones. A new native EcHsp31 structure suggests a key role of structural flexibility for chaperone function.,Quigley PM, Korotkov K, Baneyx F, Hol WG Protein Sci. 2004 Jan;13(1):269-77. PMID:14691241[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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