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- 주제어 : HslU (검색결과 5 건)
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Cleavage-Dependent Activation of ATP-Dependent Protease HslUV from Staphylococcus aureus
정소연,안진숙,권애란,하남출 한국분자세포생물학회 2020 Molecules and cells Vol.43 No.8
HslUV is a bacterial heat shock protein complex consisting of the AAA+ ATPase component HslU and the protease component HslV. HslV is a threonine (Thr) protease employing the N-terminal Thr residue in the mature protein as the catalytic residue. To date, HslUV from Gram-negative bacteria has been extensively studied. However, the mechanisms of action and activation of HslUV from Gram-positive bacteria, which have an additional N-terminal sequence before the catalytic Thr residue, remain to be revealed. In this study, we determined the crystal structures of HslV from the Gram-positive bacterium Staphylococcus aureus with and without HslU in the crystallization conditions. The structural comparison suggested that a structural transition to the symmetric form of HslV was triggered by ATP-bound HslU. More importantly, the additional N-terminal sequence was cleaved in the presence of HslU and ATP, exposing the Thr9 residue at the N-terminus and activating the ATP-dependent protease activity. Further biochemical studies demonstrated that the exposed N-terminal Thr residue is critical for catalysis with binding to the symmetric HslU hexamer. Since eukaryotic proteasomes have a similar additional N-terminal sequence, our results will improve our understanding of the common molecular mechanisms for the activation of proteasomes.
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Sung, Kwang Hoon,Lee, So Yeon,Song, Hyun Kyu American Society for Biochemistry and Molecular Bi 2013 The Journal of biological chemistry Vol.288 No.32
<P>In many bacteria, heat shock locus V (HslV) functions as a protease, which is activated by heat shock locus U (HslU). The primary sequence and structure of HslV are well conserved with those of the β-subunit of the 20 S proteasome core particle in eukaryotes. To date, the HslVU complex has only been characterized in the prokaryotic system. Recently, however, the coexistence of a 20 S proteasome with HslV protease in the same living organism has been reported. In <I>Trypanosoma brucei</I>, a protozoan parasite that causes human sleeping sickness in Africa, HslV is localized in the mitochondria, where it has a novel function in regulating mitochondrial DNA replication. Although the prokaryotic HslVU system has been studied extensively, little is known regarding its eukaryotic counterpart. Here, we report the biochemical characteristics of an HslVU complex from <I>T. brucei</I>. In contrast to the prokaryotic system, <I>T. brucei</I> possesses two potential HslU molecules, and we found that only one of them activates HslV. A key activating residue, Tyr<SUP>494</SUP>, was identified in HslU2 by biochemical and mutational studies. Furthermore, to our knowledge, this study is the first to report the crystal structure of a eukaryotic HslV, determined at 2.4 Å resolution. Drawing on our comparison of the biochemical and structural data, we discuss herein the differences and similarities between eukaryotic and prokaryotic HslVs.</P>
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Nucleotide-dependent control of internal strains in ring-shaped AAA+ motors.
Hwang, Wonmuk,Lang, Matthew J SPRINGER SCIENCE + BUSINESS MEDIA 2013 Cellular and molecular bioengineering Vol.6 No.1
<P>The AAA+ (ATPase Associated with various cellular Activities) machinery represents an extremely successful and widely used design plan for biological motors. Recently found crystal structures are beginning to reveal nucleotide-dependent conformational changes in the canonical hexameric rings of the AAA+ motors. However, the physical mechanism by which ATP binding on one subunit allosterically propagates across the entire ring remains to be found. Here we analyze and compare structural organization of three ring-shaped AAA+ motors, ClpX, HslU, and dynein. By constructing multimers using subunits of identical conformations, we find that individual subunits locally possess helical geometries with varying pitch, radius, chirality, and symmetry number. These results suggest that binding of an ATP to a subunit imposes conformational constraint that must be accommodated by more flexible nucleotide-free subunits to relieve mechanical strain on the ring. Local deformation of the ring contour and subsequent propagation of strains may be a general strategy that AAA+ motors adopt to generate force while achieving functional diversity.</P>
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Oligomeric Structure of the ATP-dependent Protease La (Lon) of Escherichia coli
박성철,Baolei Jia,양재경,Duyet Le Van,Yong Gi Shao,한상우,전영주,정진하,정강원 한국분자세포생물학회 2006 Molecules and cells Vol.21 No.1
Lon, also known as protease La, belongs to a class of ATP-dependent serine protease. It plays an essential role in degradation of abnormal proteins and of certain short-lived regulatory proteins, and is thought to possess a Ser-Lys catalytic dyad. To examine the structural organization of Lon, we performed an electron microscope analysis. The averaged images of Lon with end-on orientation revealed a six-membered, ringshaped structure with a central cavity. The side-on view showed a two-layered structure with an equal distribution of mass across the equatorial plane of the complex. Since a Lon subunit possesses two large regions containing nucleotide binding and proteolytic domains, each layer of the Lon hexamer appears to consist of the side projections of one of the major domains arranged in a ring. Lon showed a strong tendency to form hexamers in the presence of Mg2+, but dissociated into monomers and/or dimers in its absence. Moreover, Mg2+-dependent hexamer formation was independent of ATP. These results indicate that Lon has a hexameric ring-shaped structure with a central cavity, and that the establishment of this configuration requires Mg2+, but not ATP.
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