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Mol. Cells 2007; 23(2): 252-257

Published online April 30, 2007

© The Korean Society for Molecular and Cellular Biology

Nucleotide Triphosphates Inhibit the Degradation of Unfolded Proteins by HslV Peptidase

Jung Wook Lee, Eunyong Park, Oksun Bang, Soo-Hyun Eom, Gang-Won Cheong, Chin Ha Chung, Jae Hong Seol

Abstract

Escherichia coli HslVU is an ATP-dependent protease consisting of two heat shock proteins, the HslU ATPase and HslV peptidase. In the reconstituted enzyme, HslU stimulates the proteolytic activity of HslV by one to two orders of magnitude, while HslV increases the rate of ATP hydrolysis by HslU several-fold. Here we show that HslV alone can efficiently degrade certain unfolded proteins, such as unfolded lactalbumin and lysozyme prepared by complete reduction of disulfide bonds, but not their native forms. Furthermore, HslV alone cleaved a lactalbumin fragment sandwiched by two thioredoxin molecules, indicating that it can hydrolyze the internal peptide bonds of lactalbumin. Surprisingly, ATP inhibited the degradation of unfolded proteins by HslV. This inhibitory effect of ATP was markedly diminished by substitution of the Arg86 residue located in the apical pore of HslV with Gly, suggesting that interaction of ATP with the Arg residue blocks access of unfolded proteins to the proteolytic chamber of HslV. These results suggest that uncomplexed HslV is inactive under normal conditions, but may can degrade unfolded proteins when the ATP level is low, as it is during carbon starvation.

Keywords ATP-dependent Protease; ATPase; HslU;, HslV; Lactalbumin; Unfolded Proteins

Article

Research Article

Mol. Cells 2007; 23(2): 252-257

Published online April 30, 2007

Copyright © The Korean Society for Molecular and Cellular Biology.

Nucleotide Triphosphates Inhibit the Degradation of Unfolded Proteins by HslV Peptidase

Jung Wook Lee, Eunyong Park, Oksun Bang, Soo-Hyun Eom, Gang-Won Cheong, Chin Ha Chung, Jae Hong Seol

Abstract

Escherichia coli HslVU is an ATP-dependent protease consisting of two heat shock proteins, the HslU ATPase and HslV peptidase. In the reconstituted enzyme, HslU stimulates the proteolytic activity of HslV by one to two orders of magnitude, while HslV increases the rate of ATP hydrolysis by HslU several-fold. Here we show that HslV alone can efficiently degrade certain unfolded proteins, such as unfolded lactalbumin and lysozyme prepared by complete reduction of disulfide bonds, but not their native forms. Furthermore, HslV alone cleaved a lactalbumin fragment sandwiched by two thioredoxin molecules, indicating that it can hydrolyze the internal peptide bonds of lactalbumin. Surprisingly, ATP inhibited the degradation of unfolded proteins by HslV. This inhibitory effect of ATP was markedly diminished by substitution of the Arg86 residue located in the apical pore of HslV with Gly, suggesting that interaction of ATP with the Arg residue blocks access of unfolded proteins to the proteolytic chamber of HslV. These results suggest that uncomplexed HslV is inactive under normal conditions, but may can degrade unfolded proteins when the ATP level is low, as it is during carbon starvation.

Keywords: ATP-dependent Protease, ATPase, HslU,, HslV, Lactalbumin, Unfolded Proteins

Mol. Cells
Nov 30, 2022 Vol.45 No.11, pp. 763~867
COVER PICTURE
Naive (cyan) and axotomized (magenta) retinal ganglion cell axons in Xenopus tropicalis (Choi et al., pp. 846-854).

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