The Essential Role of the Flexible Termini in the Temperature-responsiveness of the Oligomeric State and Chaperone-like Activity for the Polydisperse Small Heat Shock Protein IbpB from Escherichia coli

Wei, Jiao; Qian, Mengding; Li, Pulin; Zhao, Lei; Chang, Zengyi

doi:10.1016/j.jmb.2005.01.029

Cited by 60 publications

(89 citation statements)

References 54 publications

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“…We have also observed that HdeA appears to be completely incapable of suppressing the thermal aggregation of ADH and the aggregation of insulin induced by dithiothreitol (data not shown), both of which are typically effectively suppressed by other molecular chaperones (22,23).…”

Section: Hdea Exhibits Chaperone-like Activity Exclusively At Phmentioning

confidence: 77%

“…We have provided evidence in a series of studies that molecular chaperones, at least of the small heat shock family, are able to modulate their chaperone activity via oligomeric dissociation (22,23). HdeA appears to employ a markedly different strategy for modulating its chaperone activity: it possesses an ordered conformation that is unable to bind denatured substrate proteins under normal physiological conditions (i.e.…”

Section: Discussionmentioning

confidence: 99%

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Periplasmic Protein HdeA Exhibits Chaperone-like Activity Exclusively within Stomach pH Range by Transforming into Disordered Conformation

Hong

Wei

et al. 2005

Journal of Biological Chemistry

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124

212

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The extremely acidic environment of the mammalian stomach, with a pH range usually between 1 and 3, represents a stressful challenge for enteric pathogenic bacteria such as Escherichia coli before they enter into the intestine. The hdeA gene of E. coli was found to be acid inducible and was revealed by genetic studies to be important for the acid survival of the strain. This study was performed in an attempt to characterize the mechanism of the activity of the HdeA protein. Our data provided in this report strongly suggest that HdeA employs a novel strategy to modulate its chaperone activity: it possesses an ordered conformation that is unable to bind denatured substrate proteins under normal physiological conditions (i.e. at neutral pH) and transforms into a globally disordered conformation that is able to bind substrate proteins under stress conditions (i.e. at a pH below 3). Furthermore, our data indicate that HdeA exposes hydrophobic surfaces that appear to be involved in the binding of denatured substrate proteins at extremely low pH values. In light of our observations, models are proposed to explain the action of HdeA in both a physiological and a molecular context.

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Section: Hdea Exhibits Chaperone-like Activity Exclusively At Phmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Periplasmic Protein HdeA Exhibits Chaperone-like Activity Exclusively within Stomach pH Range by Transforming into Disordered Conformation

Hong

Wei

et al. 2005

Journal of Biological Chemistry

Self Cite

124

212

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show abstract

“…However, unlike these other chaperones, which have distinct substrate binding regions, we can conclude that sHSPs rely on multiple contact sites distributed throughout the protein to protect substrates from irreversible aggregation. It is notable that the N-terminal arm of the sHSPs, apparently so critical to substrate interactions, represents an extensive, intrinsically unstructured domain (9,10,28,37). A considerable body of evidence indicates that intrinsically unstructured regions of proteins play key roles in protein-protein interactions (38,39).…”

Section: Discussionmentioning

confidence: 99%

Substrate binding site flexibility of the small heat shock protein molecular chaperones

Jaya

García

Vierling

2009

Proc. Natl. Acad. Sci. U.S.A.

217

190

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Small heat shock proteins (sHSPs) serve as a first line of defense against stress-induced cell damage by binding and maintaining denaturing proteins in a folding-competent state. In contrast to the well-defined substrate binding regions of ATP-dependent chaperones, interactions between sHSPs and substrates are poorly understood. Defining substrate-binding sites of sHSPs is key to understanding their cellular functions and to harnessing their aggregation-prevention properties for controlling damage due to stress and disease. We incorporated a photoactivatable cross-linker at 32 positions throughout a well-characterized sHSP, dodecameric PsHsp18.1 from pea, and identified direct interaction sites between sHSPs and substrates. Model substrates firefly luciferase and malate dehydrogenase form strong contacts with multiple residues in the sHSP N-terminal arm, demonstrating the importance of this flexible and evolutionary variable region in substrate binding. Within the conserved ␣-crystallin domain both substrates also bind the ␤-strand (␤7) where mutations in human homologs result in inherited disease. Notably, these binding sites are poorly accessible in the sHSP atomic structure, consistent with major structural rearrangements being required for substrate binding. Detectable differences in the pattern of cross-linking intensity of the two substrates and the fact that substrates make contacts throughout the sHSP indicate that there is not a discrete substrate binding surface. Our results support a model in which the intrinsicallydisordered N-terminal arm can present diverse geometries of interaction sites, which is likely critical for the ability of sHSPs to protect efficiently many different substrates.alpha-crystallin ͉ cross-linking ͉ intrinsic disorder ͉ P-benzoylphenylalanine ͉ protein-protein interactions

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“…20,32 Although little is known about the mechanism or kinetics of this process, increasing evidence suggests that subunit exchange is essential for chaperone activity. [33][34][35] To determine if this relationship is also exhibited by Hsp27, the subunit exchange kinetics of wild-type Hsp27 were compared to those of the deletion variants. The protocol for fluorescence resonance energy transfer (FRET) experiments reported previously to study the subunit exchange kinetics of Hsp27 32,36 was used in this study.…”

Section: Subunit Exchangementioning

confidence: 99%

Roles of the N‐ and C‐terminal sequences in Hsp27 self‐association and chaperone activity

Lelj-Garolla

Mauk

2011

Protein Science

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The small heat shock protein 27 (Hsp27 or HSPB1) is an oligomeric molecular chaperone in vitro that is associated with several neuromuscular, neurological, and neoplastic diseases. Although aspects of Hsp27 biology are increasingly well known, understanding of the structural basis for these involvements or of the functional properties of the protein remains limited. As all 11 human small heat shock proteins (sHsps) possess an a-crystallin domain, their varied functional and physiological characteristics must arise from contributions of their nonconserved sequences. To evaluate the role of two such sequences in Hsp27, we have studied three Hsp27 truncation variants to assess the functional contributions of the nonconserved N-and C-terminal sequences. The N-terminal variants D1-14 and D1-24 exhibit little chaperone activity, somewhat slower but temperature-dependent subunit exchange kinetics, and temperature-independent self-association with formation of smaller oligomers than wild-type Hsp27. The C-terminal truncation variants exhibit chaperone activity at 40°C but none at 20°C, limited subunit exchange, and temperatureindependent self-association with an oligomer distribution at 40°C that is very similar to that of wild-type Hsp27. We conclude that more of the N-terminal sequence than simply the WPDF domain is essential in the formation of larger, native-like oligomers after binding of substrate and/or in binding of Hsp27 to unfolding peptides. On the other hand, the intrinsically flexible C-terminal region drives subunit exchange and thermally-induced unfolding, both of which are essential to chaperone activity at low temperature and are linked to the temperature dependence of Hsp27 self-association.

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The Essential Role of the Flexible Termini in the Temperature-responsiveness of the Oligomeric State and Chaperone-like Activity for the Polydisperse Small Heat Shock Protein IbpB from Escherichia coli

Cited by 60 publications

References 54 publications

Periplasmic Protein HdeA Exhibits Chaperone-like Activity Exclusively within Stomach pH Range by Transforming into Disordered Conformation

Periplasmic Protein HdeA Exhibits Chaperone-like Activity Exclusively within Stomach pH Range by Transforming into Disordered Conformation

Substrate binding site flexibility of the small heat shock protein molecular chaperones

Roles of the N‐ and C‐terminal sequences in Hsp27 self‐association and chaperone activity

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