Small heat shock protein AgsA forms dynamic fibrils

Abstract

Edited by Miguel De la Rosa Keywords:Small heat shock protein Chaperone Fibril Amyloid Electron microscopy Cryo-electron tomography a b s t r a c t As a class of molecular chaperones, small heat shock proteins (sHsps) usually exist as multi-subunit spherical oligomers. In this study, we report that AgsA, a sHsp of Salmonella enterica serovar Typhimurium, spontaneously forms fibrils in vitro. These fibrils tend to be formed at elevated temperature and do not share the characteristics of amyloid. Interestingly, the fibril-forming AgsA is able to suppress the dithiothreitol-induced aggregation of insulin efficiently within a certain range of temperature. During this process, AgsA fibrils disappear and spherical complexes form between AgsA and insulin molecules. These data suggest that AgsA fibrils may represent a distinctive type of structural and functional form of sHsp from spherical oligomers. Our study provides new insights into sHsp structures and chaperone functions. Structured summary of protein interactions:AgsA and AgsA bind by electron microscopy (View interaction). Insulin and Insulin bind by molecular sieving (View interaction). Insulin and Insulin bind by electron microscopy (View interaction). AgsA and AgsA bind by molecular sieving (View interaction). AgsA and AgsA bind by fluorescence technology (View interaction). AgsA and AgsA bind by circular dichroism (View interaction). Insulin and Insulin bind by fluorescence technology (View interaction). AgsA and Insulin bind by molecular sieving (View interaction). AgsA and AgsA bind by electron tomography (View interaction).

A Small Heat Shock Protein Enables Escherichia coli To Grow at a Lethal Temperature of 50 C Conceivably by Maintaining Cell Envelope Integrity

“…Uniquely, the sHSPs of both prokaryotic and eukaryotic sources have also been found to be associated with cell membranes (34)(35)(36)(37)(38). Over the years, we have tried to delineate the function and mechanism of sHSPs, from largely bacterial sources, via both in vitro and in vivo studies (39)(40)(41)(42)(43)(44)(45). To study the function and mechanism of sHSPs in C. elegans, we first focused on CeHSP17, which remains the least characterized such proteins in terms of function and properties among the small heat shock proteins of C. elegans (46) and is predicted by our bioinformatics analysis to be putatively localized in mitochondria (Table 1 ).…”

Insights into How Small Heat Shock Proteins Bind a Great Diversity of Substrate Proteins: A Super-Transformer Model

“…The most important structural feature of sHSPs is that they exclusively exist as multi-subunit oligomers, which had been observed 40 years ago on mammalian sHSPs (α-crystallin and Hsp27) (Spector et al 1971 ;Arrigo and Welch 1987 ;Longoni et al 1990 ) and later on many sHSPs from different organisms (Chang et al 1996 ;Haley et al 2000 ;Kim et al 1998 ;van Montfort et al 2001 ;de Miguel et al 2009 ;den Engelsman et al 2009 ;Haslbeck et al 1999Haslbeck et al , 2008Kennaway et al 2005 ;Shi et al 2011 ;Leroux et al, 1997b ;Giese and Vierling 2004 ;Sun et al 2004 ;Hilario et al 2011 ;Hockertz et al 1991 ;Merck et al 1993b ). Although subunits within a sHSP oligomer are theoretically identical in their substrate-binding residues, the architecture of such multi-subunits would enable the sHSP oligomer to incorporate substrate proteins at multiple independent sites.…”

“…My colleagues and I have focused on sHSPs for years and investigated their chaperone function and mechanism under both in vitro (Chang et al 1996 ;Yang et al 1999 ;Gu et al 2002 ;Fu et al 2005 ;Jiao et al 2005bJiao et al , 2008Shi et al 2011 ) and in vivo (Jiao et al 2005a ;Ezemaduka et al 2014 ;Fu et al 2013b ) conditions. One intriguing feature of sHSPs, in our opinion, is that they are able to recognize and bind a great diversity of substrate proteins (Bepperling et al 2012 ;Basha et al 2004 ;Fu 2014 ).…”

Understanding What Small Heat Shock Proteins Do for Bacterial Cells

“…Bacterial small heat shock proteins forming homo-oligomers of a diversity of sizes include, for example, the IbpB (Veinger et al 1998 ;Kitagawa et al 2002 ;Jiao et al 2005 ) and IbpA (Matuszewska et al 2005 ;Ratajczak et al 2010 ) of E. coli cells. Under stress conditions, bacterial sHSPs have been observed to form supermolecular assemblies in the form of fi brils (Ratajczak et al 2010 ;Shi et al 2011 ), which was the form that bound unfolded client proteins. Given that small heat shock proteins have been observed to form large granules in animal cells under heat shock conditions (Arrigo et al 1988 ;Collier et al 1988 ), it would be interesting to fi nd out whether such large assemblies are the functional forms of small heat shock proteins in bacterial cells.…”

“…The major biological properties characteristic of bacterial small heat shock proteins include the following: First, they form dynamic oligomers (Chang et al 1996 ;Shearstone and Baneyx 1999 ;Jiao et al 2005 ;Kennaway et al 2005 ;Ratajczak et al 2010 ;Shi et al 2011 ), a feature essential for their functioning (Gu et al 2002 ;Zhang et al 2005 ). Second, they exhibit effective chaperone-like activities to suppress the aggregation of non-native client proteins under in vitro (Veinger et al 1998 ;Kitagawa et al 2002 ;Jiao et al 2005 ;Matuszewska et al 2005 ) or in vivo conditions (Veinger et al 1998 ;Mogk et al 2003b ;Fu et al 2013a , b ).…”