7T56

Cryo-EM structure of PCAT1 in the inward-facing intermediate conformation under ATP turnover condition


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.70 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 

Starting Model: experimental
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wwPDB Validation   3D Report Full Report


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Literature

Structures of the peptidase-containing ABC transporter PCAT1 under equilibrium and nonequilibrium conditions.

Kieuvongngam, V.Chen, J.

(2022) Proc Natl Acad Sci U S A 119

  • DOI: https://doi.org/10.1073/pnas.2120534119
  • Primary Citation of Related Structures:  
    7T54, 7T55, 7T56, 7T57

  • PubMed Abstract: 

    ATP-binding cassette (ABC) transporters are ubiquitous molecular pumps that transport a broad range of substrates across biological membranes. Although the structure and function of ABC transporters has been studied extensively, our understanding of their energetics and dynamics remains limited. Here, we present studies of the peptidase-containing ABC transporter 1 (PCAT1), a polypeptide processing and secretion ABC transporter that functions via the classic alternating access mechanism. PCAT1 is a homodimer containing two peptidase (PEP) domains, two transmembrane domains, and two nucleotide-binding domains (NBDs). Using cryo-electron microscopy, we analyzed the structures of wild-type PCAT1 under conditions that either prevent or permit ATP hydrolysis and observed two completely different conformational distributions. In the presence of ATP but absence of Mg 2+ , PCAT1 adopts an NBD-dimerized, outward-facing conformation. The two PEP domains are dissociated from the transporter core, preventing uncoupled substrate cleavage. The addition of Mg 2+ to promote ATP hydrolysis shifts the majority of the particles into NBD-separated, inward-facing conformations. Under this ATP turnover condition, only a small fraction of PCAT1 adopts the NBD-dimerized conformation. These data give rise to two mechanistic conclusions: 1) the ATP-bound, NBD-dimerized conformation is the lowest energy state, and 2) the rate-limiting step in the PCAT1 transport cycle is the formation of the NBD dimer. The thermodynamic conclusion is likely a general property shared by many ABC transporters. The kinetic bottleneck, however, varies from transporter to transporter.


  • Organizational Affiliation

    Laboratory of Membrane Biology and Biophysics, The Rockefeller University, New York, NY 10065.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
ABC-type bacteriocin transporterA,
C [auth B]
730Acetivibrio thermocellusMutation(s): 0 
Gene Names: Cthe_0534
Membrane Entity: Yes 
UniProt
Find proteins for A3DCU1 (Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372))
Explore A3DCU1 
Go to UniProtKB:  A3DCU1
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA3DCU1
Sequence Annotations
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
PCAT1 peptide substrateB [auth C],
D
93Acetivibrio thermocellusMutation(s): 0 
Gene Names: Cthe_0535
UniProt
Find proteins for A3DCU2 (Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372))
Explore A3DCU2 
Go to UniProtKB:  A3DCU2
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA3DCU2
Sequence Annotations
Expand
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 3.70 Å
  • Aggregation State: PARTICLE 
  • Reconstruction Method: SINGLE PARTICLE 
EM Software:
TaskSoftware PackageVersion
MODEL REFINEMENTCoot0.8.9.2
RECONSTRUCTIONcryoSPARC3.0

Structure Validation

View Full Validation Report



Entry History & Funding Information

Deposition Data


Funding OrganizationLocationGrant Number
Howard Hughes Medical Institute (HHMI)United States--

Revision History  (Full details and data files)

  • Version 1.0: 2022-02-09
    Type: Initial release
  • Version 1.1: 2024-02-28
    Changes: Data collection, Refinement description, Structure summary