Crystal Structure of a Mammalian Cytidylyltransferase

Experimental Data Snapshot

  • Resolution: 3.00 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.223 
  • R-Value Observed: 0.226 

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This is version 1.3 of the entry. See complete history


Structural Basis for Autoinhibition of CTP:Phosphocholine Cytidylyltransferase (CCT), the Regulatory Enzyme in Phosphatidylcholine Synthesis, by Its Membrane-binding Amphipathic Helix.

Lee, J.Taneva, S.G.Holland, B.W.Tieleman, D.P.Cornell, R.B.

(2014) J Biol Chem 289: 1742-1755

  • DOI: https://doi.org/10.1074/jbc.M113.526970
  • Primary Citation of Related Structures:  
    4MVC, 4MVD

  • PubMed Abstract: 

    CTP:phosphocholine cytidylyltransferase (CCT) interconverts between an inactive soluble and active membrane-bound form in response to changes in membrane lipid composition. Activation involves disruption of an inhibitory interaction between the αE helices at the base of the active site and an autoinhibitory (AI) segment in the regulatory M domain and membrane insertion of the M domain as an amphipathic helix. We show that in the CCT soluble form the AI segment functions to suppress kcat and elevate the Km for CTP. The crystal structure of a CCT dimer composed of the catalytic and AI segments reveals an AI-αE interaction as a cluster of four amphipathic helices (two αE and two AI helices) at the base of the active sites. This interaction corroborates mutagenesis implicating multiple hydrophobic residues within the AI segment that contribute to its silencing function. The AI-αE interaction directs the turn at the C-terminal end of the AI helix into backbone-to-backbone contact with a loop (L2) at the opening to the active site, which houses the key catalytic residue, lysine 122. Molecular dynamics simulations suggest that lysine 122 side-chain orientations are constrained by contacts with the AI helix-turn, which could obstruct its engagement with substrates. This work deciphers how the CCT regulatory amphipathic helix functions as a silencing device.

  • Organizational Affiliation

    From the Departments of Molecular Biology and Biochemistry and.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Choline-phosphate cytidylyltransferase A
A, B
300Rattus norvegicusMutation(s): 0 
Gene Names: CtpctPcyt1Pcyt1a
Find proteins for P19836 (Rattus norvegicus)
Explore P19836 
Go to UniProtKB:  P19836
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP19836
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on CDC

Download Ideal Coordinates CCD File 
C [auth A],
D [auth B]
C14 H26 N4 O11 P2
Experimental Data & Validation

Experimental Data

  • Resolution: 3.00 Å
  • R-Value Free: 0.288 
  • R-Value Work: 0.223 
  • R-Value Observed: 0.226 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 87.26α = 90
b = 44.55β = 111.21
c = 97.13γ = 90
Software Package:
Software NamePurpose
MXdata collection
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-12-11
    Type: Initial release
  • Version 1.1: 2014-02-05
    Changes: Database references
  • Version 1.2: 2017-08-09
    Changes: Refinement description, Source and taxonomy
  • Version 1.3: 2023-09-20
    Changes: Data collection, Database references, Derived calculations, Refinement description