Cytoplasmic Chaperonin Containing TCP-1:  Structural and Functional Characterization

Melki, Ronald; Batelier, Gérard; Soulié, Stéphanie; Williams, Robley C.

doi:10.1021/bi962830o

Cited by 106 publications

(115 citation statements)

References 53 publications

Supporting

Mentioning

105

Contrasting

Order By: Relevance

“…Several earlier studies suggested that the conformation of the eukaryotic cytosolic chaperonin in the presence of MgATP is different from that observed in its absence (Gao et al, 1992;Marco et al, 1994;Melki & Cowan, 1994;Hynes et al, 1995;Roseman et al, 1996;Melki et al, 1997).…”

Section: Discussionmentioning

confidence: 95%

“…It has been suggested that the subunits of the heterooligomeric cytosolic chaperonin may have evolved to achieve high specificity for cytoskeletal proteins. It has been demonstrated recently that the narrow specificity of CCT might be due to relatively high cellular concentration of actin and tubulin, which mask its interaction with other proteins (Melki et al, 1997). However, it remains to be demonstrated whether the folding of other proteins that bind to CCT is also facilitated by it.…”

mentioning

confidence: 99%

“…More recently, ultracentrifugation studies confirmed significant differences in shape of the rabbit CCT in the presence and absence of nucleotides and a protein substrate. These studies suggested that the ATP-CCT complex is more compact than the ADP-CCT complex (Melki et al, 1997).…”

mentioning

confidence: 99%

See 2 more Smart Citations

MgATP binding to the nucleotide‐binding domains of the eukaryotic cytoplasmic chaperonin induces conformational changes in the putative substrate‐binding domains

et al. 1998

View full text Add to dashboard Cite

The eukaryotic cytosolic chaperonins are large heterooligomeric complexes with a cylindrical shape, resembling that of the homooligomeric bacterial counterpart, GroEL. In analogy to GroEL, changes in shape of the cytosolic chaperonin have been detected in the presence of MgATP using electron microscopy but, in contrast to the nucleotide-induced conformational changes in GroEL, no details are available about the specific nature of these changes. The present study identifies the structural regions of the cytosolic chaperonin that undergo conformational changes when MgATP binds to the nucleotide binding domains. It is shown that limited proteolysis with trypsin in the absence of MgATP cleaves each of the eight subunits approximately in half, generating two fragments of -30 kDa. Using mass spectrometry (MS) and N-terminal sequence analysis, the cleavage is found to occur in a narrow span of the amino acid sequence, corresponding to the peptide binding regions of GroEL and to the helical protrusion, recently identified in the structure of the substrate binding domain of the archeal group I1 chaperonin. This proteolytic cleavage is prevented by MgATP but not by ATP in the absence of magnesium, ATP analogs (MgATPyS and MgAMP-PNP) or MgADP. These results suggest that, in analogy to GroEL, binding of MgATP to the nucleotide binding domains of the cytosolic chaperonin induces long range conformational changes in the polypeptide binding domains. It is postulated that despite their different subunit composition and substrate specificity, group I and group I1 chaperonins may share similar, functionally-important, conformational changes. Additional conformational changes are likely to involve a flexible helix-loop-helix motif, which is characteristic for all group I1 chaperonins. Keywords: CCT; limited proteolysis; long-range conformational changes; mass spectrometryChaperonins are a family of large, sequence-related, oligomeric complexes found in chloroplasts, mitochondria and eubacteria (Group I chaperonins, or GroE subclass, represented by GroEL), and in archaebacteria and eukaryotic cytosol (Group I1 chaperonins or TCP-I subclass) (Ellis, 1996). The structure of the chaperonins consists of two stacked rings of 7-9 subunits, with a large

show abstract

Section: Discussionmentioning

confidence: 95%

mentioning

confidence: 99%

See 1 more Smart Citation

MgATP binding to the nucleotide‐binding domains of the eukaryotic cytoplasmic chaperonin induces conformational changes in the putative substrate‐binding domains

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Amino acid residues within the ring make contacts with the unfolded protein and decrease the activation energy required to form the three-dimensional structure of the native protein [73]. Each CCT subunit binds ATP and uses the energy of ATP hydrolysis to drive the folding process [74,75]. Actin and tubulin are major cellular proteins that require CCT to fold, but other substrates have been described.…”

Section: Over-turning the Paradigm -Phlp1 As An Essential Co-chaperonmentioning

confidence: 99%

Function of phosducin-like proteins in G protein signaling and chaperone-assisted protein folding

Willardson

Howlett

2007

Cellular Signalling

100

101

View full text Add to dashboard Cite

Members of the phosducin gene family were initially proposed to act as down-regulators of G protein signaling by binding G protein βγ dimers (Gβγ) and inhibiting their ability to interact with G protein α subunits (Gα) and effectors. However, recent findings have overturned this hypothesis by showing that most members of the phosducin family act as cochaperones with the cytosolic chaperonin complex (CCT) to assist in the folding of a variety of proteins from their nascent polypeptides. In fact rather than inhibiting G protein pathways, phosducin-like protein 1 (PhLP1) has been shown to be essential for G protein signaling by catalyzing the folding and assembly of the Gβγ dimer. PhLP2 and PhLP3 have no role in G protein signaling, but they appear to assist in the folding of proteins essential in regulating cell cycle progression as well as actin and tubulin. Phosducin itself is the only family member that does not participate with CCT in protein folding, but it is believed to have a specific role in visual signal transduction to chaperone Gβγ subunits as they translocate to and from the outer and inner segments of photoreceptor cells during light-adaptation.

show abstract

“…GST alone, used as a control, was expressed and purified exactly as for GST-PhLP2A. CCT was purified from rabbit reticulocyte lysate as described previously (Gao et al, 1992;Melki et al, 1997). …”

mentioning

confidence: 99%

Functional Interaction between Phosducin-like Protein 2 and Cytosolic Chaperonin Is Essential for Cytoskeletal Protein Function and Cell Cycle Progression

Stirling

Srayko

Takhar

et al. 2007

MBoC

View full text Add to dashboard Cite

The Chaperonin Containing Tcp1 (CCT) maintains cellular protein folding homeostasis in the eukaryotic cytosol by assisting the biogenesis of many proteins, including actins, tubulins, and regulators of the cell cycle. Here, we demonstrate that the essential and conserved eukaryotic phosducin-like protein 2 (PhLP2/PLP2) physically interacts with CCT and modulates its folding activity. Consistent with this functional interaction, temperature-sensitive alleles of Saccharomyces cerevisiae PLP2 exhibit cytoskeletal and cell cycle defects. We uncovered several high-copy suppressors of the plp2 alleles, all of which are associated with G1/S cell cycle progression but which do not appreciably affect cytoskeletal protein function or fully rescue the growth defects. Our data support a model in which Plp2p modulates the biogenesis of several CCT substrates relating to cell cycle and cytoskeletal function, which together contribute to the essential function of PLP2. INTRODUCTIONPhosducin-like proteins (PhLPs) are a conserved family of small thioredoxin-like proteins that were originally identified as modulators of heterotrimeric G protein signaling in the retina (Schroder and Lohse, 1996). Subsequently, they were shown to have roles in G protein signaling in other cell types as well as having G protein-independent functions (Flanary et al., 2000;Blaauw et al., 2003). One of the other functions of PhLPs is the regulation of the eukaryotic protein-folding machine known as Chaperonin Containing Tcp1 (CCT; also called TCP1-containing Ring Complex [TRiC]) (McLaughlin et al., 2002;Martín-Benito et al., 2004;Lukov et al., 2005Lukov et al., , 2006Stirling et al., 2006).Chaperonins are oligomeric molecular chaperones that bind nonnative proteins and facilitate their transition to the native state (Hartl and Hayer-Hartl, 2002). These barrelshaped molecular machines undergo large conformational changes to encapsulate and release bound substrate proteins during their ATP-dependent folding cycle (Spiess et al., 2004). In the eukaryotic cytosol, the chaperonin CCT ensures the correct folding and assembly of a variety of proteins. The best-characterized substrates of CCT are actins and tubulins, although several recent studies have extended the number of known CCT substrates, including several cell cycle proteins (Thulasiraman et al., 1999;Camasses et al., 2003; Siegers et al., 2003; for review, see Spiess et al., 2004). CCT cooperates with another chaperone called Prefoldin (PFD) in the folding of actins and tubulins (Geissler et al., 1998;Vainberg et al., 1998). PFD uses six long coiled-coil "tentacles" to stabilize substrate proteins at the opening of its jellyfish-shaped cavity before their delivery to the open CCT cavity (Vainberg et al., 1998;Siegers et al., 1999;Siegert et al., 2000;Lundin et al., 2004). Together, PFD and CCT compose a folding pathway for cytoskeletal proteins, which, along with PhLPs, control the folding of actin and tubulin (Siegers et al., 1999;Lacefield and Solomon, 2003;Stirling et al., 2006).PhLPs can be sub...

show abstract

Cytoplasmic Chaperonin Containing TCP-1: Structural and Functional Characterization

Cited by 106 publications

References 53 publications

MgATP binding to the nucleotide‐binding domains of the eukaryotic cytoplasmic chaperonin induces conformational changes in the putative substrate‐binding domains

MgATP binding to the nucleotide‐binding domains of the eukaryotic cytoplasmic chaperonin induces conformational changes in the putative substrate‐binding domains

Function of phosducin-like proteins in G protein signaling and chaperone-assisted protein folding

Functional Interaction between Phosducin-like Protein 2 and Cytosolic Chaperonin Is Essential for Cytoskeletal Protein Function and Cell Cycle Progression

Contact Info

Product

Resources

About