1AYI

COLICIN E7 IMMUNITY PROTEIN IM7


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.178 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

A structural comparison of the colicin immunity proteins Im7 and Im9 gives new insights into the molecular determinants of immunity-protein specificity.

Dennis, C.A.Videler, H.Pauptit, R.A.Wallis, R.James, R.Moore, G.R.Kleanthous, C.

(1998) Biochem.J. 333 ( Pt 1): 183-191


  • PubMed Abstract: 
  • We report the first detailed comparison of two immunity proteins which, in conjunction with recent protein engineering data, begins to explain how these structurally similar proteins are able to bind and inhibit the endonuclease domain of colicin E9 ...

    We report the first detailed comparison of two immunity proteins which, in conjunction with recent protein engineering data, begins to explain how these structurally similar proteins are able to bind and inhibit the endonuclease domain of colicin E9 (E9 DNase) with affinities that differ by 12 orders of magnitude. In the present work, we have determined the X-ray structure of the Escherichia coli colicin E7 immunity protein Im7 to 2.0 A resolution by molecular replacement, using as a trial model the recently determined NMR solution structure of Im9. Whereas the two proteins adopt similar four-helix structures, subtle structural differences, in particular involving a conserved tyrosine residue critical for E9 DNase binding, and the identity of key residues in the specificity helix, lie at the heart of their markedly different ability to bind the E9 DNase. Two other crystal structures were reported recently for Im7; in one, Im7 was a monomer and was very similar to the structure reported here, whereas in the other it was a dimer to which functional significance was assigned. Since this previous work suggested that Im7 could exist either as a monomer or a dimer, we used analytical ultracentrifugation to investigate this question further. Under a variety of solution conditions, we found that Im7 only ever exists in solution as a monomer, even up to protein concentrations of 15 mg/ml, casting doubt on the functional significance of the crystallographically observed dimer. This work provides a structural framework with which we can understand immunity-protein specificity, and in addition we believe it to be the first successfully refined crystal structure solved by molecular replacement using an NMR trial model with less than 100% sequence identity.


    Organizational Affiliation

    School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, U.K.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
COLICIN E IMMUNITY PROTEIN 7
A
87Escherichia coliGene Names: imm (ceiE7)
Find proteins for Q03708 (Escherichia coli)
Go to UniProtKB:  Q03708
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.178 
  • Space Group: I 2 2 2
Unit Cell:
Length (Å)Angle (°)
a = 44.630α = 90.00
b = 50.677β = 90.00
c = 75.187γ = 90.00
Software Package:
Software NamePurpose
MARSCALEdata scaling
REFMACrefinement
AMoREphasing
XDSdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1998-01-28
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance