3MK9

Stabilized Ricin Immunogen 1-33/44-198


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.08 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.210 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Introduction of a disulfide bond leads to stabilization and crystallization of a ricin immunogen.

Compton, J.R.Legler, P.M.Clingan, B.V.Olson, M.A.Millard, C.B.

(2011) Proteins 79: 1048-1060

  • DOI: 10.1002/prot.22933
  • Primary Citation of Related Structures:  3LC9

  • PubMed Abstract: 
  • RTA1-33/44-198 is a catalytically inactive, single-domain derivative of the ricin toxin A-chain (RTA) engineered to serve as a stable protein scaffold for presentation of native immunogenic epitopes (Olson et al., Protein Eng Des Sel 2004;17:391-397) ...

    RTA1-33/44-198 is a catalytically inactive, single-domain derivative of the ricin toxin A-chain (RTA) engineered to serve as a stable protein scaffold for presentation of native immunogenic epitopes (Olson et al., Protein Eng Des Sel 2004;17:391-397). To improve the stability and solubility of RTA1-33/44-198 further, we have undertaken the design challenge of introducing a disulfide (SS) bond. Nine pairs of residues were selected for placement of the SS-bond based on molecular dynamics simulation studies of the modeled single-domain chain. Disulfide formation at either of two positions (R48C/T77C or V49C/E99C) involving a specific surface loop (44-55) increased the protein melting temperature by ~5°C compared with RTA1-33/44-198 and by ~13°C compared with RTA. Prolonged stability studies of the R48C/T77C variant (> 60 days at 37°C, pH 7.4) confirmed a > 40% reduction in self-aggregation compared with RTA1-33/44-198 lacking the SS-bond. The R48C/T77C variant retained affinity for anti-RTA antibodies capable of neutralizing ricin toxin, including a monoclonal that recognizes a human B-cell epitope. Introduction of either R48C/T77C or V49C/E99C promoted crystallization of RTA1-33/44-198, and the X-ray structures of the variants were solved to 2.3 A or 2.1 A resolution, respectively. The structures confirm formation of an intramolecular SS-bond, and reveal a single-domain fold that is significantly reduced in volume compared with RTA. Loop 44 to 55 is partly disordered as predicted by simulations, and is positioned to form self-self interactions between symmetry-related molecules. We discuss the importance of RTA loop 34 to 55 as a nucleus for unfolding and aggregation, and draw conclusions for ongoing structure-based minimalist design of RTA-based immunogens.


    Organizational Affiliation

    Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Ricin
A
189Ricinus communisEC: 3.2.2.22
Find proteins for P02879 (Ricinus communis)
Go to UniProtKB:  P02879
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.08 Å
  • R-Value Free: 0.236 
  • R-Value Work: 0.210 
  • Space Group: I 2 2 2
Unit Cell:
Length (Å)Angle (°)
a = 51.744α = 90.00
b = 72.767β = 90.00
c = 96.382γ = 90.00
Software Package:
Software NamePurpose
AMoREphasing
SAINTdata reduction
SADABSdata scaling
CNSrefinement
REFMACrefinement
PROTEUM PLUSdata collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2010-11-10
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2012-01-25
    Type: Database references