The structure and evolution of eukaryotic chaperonin-containing TCP-1 and its mechanism that folds actin into a protein spring

Actin is folded to its native state in eukaryotic cytosol by the sequential allosteric mechanism of the chaperonin-containing TCP-1 (CCT). The CCT machine is a double-ring ATPase built from eight related subunits, CCT1–CCT8. Non-native actin interacts with specific subunits and is annealed slowly through sequential binding and hydrolysis of ATP around and across the ring system. CCT releases a folded but soft ATP-G-actin monomer which is trapped 80 kJ/mol uphill on the folding energy surface by its ATP-Mg2+/Ca2+ clasp. The energy landscape can be re-explored in the actin filament, F-actin, because ATP hydrolysis produces dehydrated and more compact ADP-actin monomers which, upon application of force and strain, are opened and closed like the elements of a spring. Actin-based myosin motor systems underpin a multitude of force generation processes in cells and muscles. We propose that the water surface of F-actin acts as a low-binding energy, directional waveguide which is recognized specifically by the myosin lever-arm domain before the system engages to form the tight-binding actomyosin complex. Such a water-mediated recognition process between actin and myosin would enable symmetry breaking through fast, low energy initial binding events. The origin of chaperonins and the subsequent emergence of the CCT–actin system in LECA (last eukaryotic common ancestor) point to the critical role of CCT in facilitating phagocytosis during early eukaryotic evolution and the transition from the bacterial world. The coupling of CCT-folding fluxes to the cell cycle, cell size control networks and cancer are discussed together with directions for further research.

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Toward an understanding of the Cdc48/p97 ATPase

F1000Research ◽

10.12688/f1000research.11683.1 ◽

2017 ◽

Vol 6 ◽

pp. 1318 ◽

Cited By ~ 50

Author(s):

Nicholas Bodnar ◽

Tom Rapoport

Keyword(s):

Atp Hydrolysis ◽

Critical Role ◽

Ring Structure ◽

Cellular Systems ◽

Aaa Atpase ◽

Double Ring ◽

Terminal Domain ◽

D2 Domain ◽

Central Pore

A conserved AAA+ ATPase, called Cdc48 in yeast and p97 or VCP in metazoans, plays an essential role in many cellular processes by segregating polyubiquitinated proteins from complexes or membranes. For example, in endoplasmic reticulum (ER)-associated protein degradation (ERAD), Cdc48/p97 pulls polyubiquitinated, misfolded proteins out of the ER and transfers them to the proteasome. Cdc48/p97 consists of an N-terminal domain and two ATPase domains (D1 and D2). Six Cdc48 monomers form a double-ring structure surrounding a central pore. Cdc48/p97 cooperates with a number of different cofactors, which bind either to the N-terminal domain or to the C-terminal tail. The mechanism of Cdc48/p97 action is poorly understood, despite its critical role in many cellular systems. Recent in vitro experiments using yeast Cdc48 and its heterodimeric cofactor Ufd1/Npl4 (UN) have resulted in novel mechanistic insight. After interaction of the substrate-attached polyubiquitin chain with UN, Cdc48 uses ATP hydrolysis in the D2 domain to move the polypeptide through its central pore, thereby unfolding the substrate. ATP hydrolysis in the D1 domain is involved in substrate release from the Cdc48 complex, which requires the cooperation of the ATPase with a deubiquitinase (DUB). Surprisingly, the DUB does not completely remove all ubiquitin molecules; the remaining oligoubiquitin chain is also translocated through the pore. Cdc48 action bears similarities to the translocation mechanisms employed by bacterial AAA ATPases and the eukaryotic 19S subunit of the proteasome, but differs significantly from that of a related type II ATPase, the NEM-sensitive fusion protein (NSF). Many questions about Cdc48/p97 remain unanswered, including how it handles well-folded substrate proteins, how it passes substrates to the proteasome, and how various cofactors modify substrates and regulate its function.

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Molecular Mechanism of SARS-CoVs Orf6 Targeting the Rae1–Nup98 Complex to Compete With mRNA Nuclear Export

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.813248 ◽

2022 ◽

Vol 8 ◽

Author(s):

Tinghan Li ◽

Yibo Wen ◽

Hangtian Guo ◽

Tingting Yang ◽

Haitao Yang ◽

...

Keyword(s):

Nuclear Export ◽

Rna Binding ◽

Critical Role ◽

Tight Binding ◽

Viral Proteins ◽

Interferon Signaling ◽

Binding Groove ◽

Mrna Binding ◽

Common Target

The accessory protein Orf6 is uniquely expressed in sarbecoviruses including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which is an ongoing pandemic. SARS-CoV-2 Orf6 antagonizes host interferon signaling by inhibition of mRNA nuclear export through its interactions with the ribonucleic acid export 1 (Rae1)–nucleoporin 98 (Nup98) complex. Here, we confirmed the direct tight binding of Orf6 to the Rae1-Nup98 complex, which competitively inhibits RNA binding. We determined the crystal structures of both SARS-CoV-2 and SARS-CoV-1 Orf6 C-termini in complex with the Rae1–Nup98 heterodimer. In each structure, SARS-CoV Orf6 occupies the same potential mRNA-binding groove of the Rae1–Nup98 complex, comparable to the previously reported structures of other viral proteins complexed with Rae1-Nup98, indicating that the Rae1–Nup98 complex is a common target for different viruses to impair the nuclear export pathway. Structural analysis and biochemical studies highlight the critical role of the highly conserved methionine (M58) of SARS-CoVs Orf6. Altogether our data unravel a mechanistic understanding of SARS-CoVs Orf6 targeting the mRNA-binding site of the Rae1–Nup98 complex to compete with the nuclear export of host mRNA, which further emphasizes that Orf6 is a critical virulence factor of SARS-CoVs.

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Leukotriene A4 hydrolase: a critical role of glutamic acid-296 for the binding of bestatin

Biochemical Journal ◽

10.1042/bj3450621 ◽

2000 ◽

Vol 345 (3) ◽

pp. 621-625 ◽

Cited By ~ 5

Author(s):

Martina ANDBERG ◽

Anders WETTERHOLM ◽

Juan F. MEDINA ◽

Jesper Z. HAEGGSTRÖM

Keyword(s):

Epoxide Hydrolase ◽

Critical Role ◽

Tight Binding ◽

Leukotriene B4 ◽

Catalytic Residue ◽

Ic50 Values ◽

Leukotriene A4 Hydrolase ◽

Leukotriene A4 ◽

Structural Determinant

Leukotriene A4 hydrolase is a bifunctional Zn2+-containing enzyme catalysing the formation of the potent chemotaxin leukotriene B4. From an analysis of three mutants of Glu-296 we have found that this catalytic residue is critical for the binding of bestatin, a classical aminopeptidase inhibitor. For bestatin, but not for three other tight-binding inhibitors, the IC50 values for inhibition of the epoxide hydrolase activity decreased in the mutants to 0.7-0.003% of the control. Hence Glu-296 is an important structural determinant for binding of bestatin to leukotriene A4 hydrolase; this conclusion might also apply to other members of the M1 family of metallopeptidases.

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Photoinduced charge-transfer in chromophore-labeled gold nanoclusters: quantum evidence of the critical role of ligands and vibronic couplings

Nanoscale ◽

10.1039/d1nr00213a ◽

2021 ◽

Vol 13 (14) ◽

pp. 6786-6797

Author(s):

Adrian Domínguez-Castro ◽

Carlos R. Lien-Medrano ◽

Khaoula Maghrebi ◽

Sabri Messaoudi ◽

Thomas Frauenheim ◽

...

Keyword(s):

Density Functional ◽

Critical Role ◽

Gold Nanoclusters ◽

Tight Binding ◽

Time Dependent ◽

Tight Binding Method ◽

Photo Induced Electron Transfer ◽

Vibronic Couplings ◽

Photoinduced Charge

We present the first application of the time-dependent density functional tight-binding method to rationalize the photo-induced electron transfer in an experimental hexyl-protected Au25 cluster labeled with a pyrene fluorophore.

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The Role of the SLP in Autism Spectrum Disorder Screening and Assessment

Perspectives on Language Learning and Education ◽

10.1044/lle15.2.50 ◽

2008 ◽

Vol 15 (2) ◽

pp. 50-59 ◽

Cited By ~ 1

Author(s):

Amy Philofsky

Keyword(s):

Language Development ◽

Critical Role ◽

Children With Autism ◽

Autism Spectrum ◽

Children With Asd ◽

Prevalence Estimates ◽

Notable Increase ◽

Screening Assessment ◽

Critical Components

AbstractRecent prevalence estimates for autism have been alarming as a function of the notable increase. Speech-language pathologists play a critical role in screening, assessment and intervention for children with autism. This article reviews signs that may be indicative of autism at different stages of language development, and discusses the importance of several psychometric properties—sensitivity and specificity—in utilizing screening measures for children with autism. Critical components of assessment for children with autism are reviewed. This article concludes with examples of intervention targets for children with ASD at various levels of language development.

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