User Stories:BETA-BLIP

Crystallographic details

Parameter	Value	Comment
Space Group	P3₂21	enantiomorphic with P3₁21
Unit Cell	75Å 75Å 133Å 90° 90° 120°	average
Resolution	2.5Å	average
Solvent Content	~50%	average
ASU Contents	1×BETA + 1×BLIP	protein-protein complex
Model Quality	100% identity	Both solved independently
Anomalous atoms	N/A
Wavelength	N/A

Story

The case of β-lactamase (BETA)–β-lactamase inhibitor (BLIP) has been used repeatedly as a test case for Phaser because the original structure solution by MR using AMoRe was difficult even though good models were available (the structures of both components had already been solved in isolation). The difficult part of the MR solution was placing BLIP. Phaser rapidly produces a correct solution for the complex.

This previously difficult structure solution becomes trivial because of two algorithms implemented in Phaser.

• The anisotropy correction; there is significant anisotropy in the data (the maximum B-factor difference in different directions is 32 Ų).
• The improved rotation-function target in MLRF, particularly in that the solution for BETA can be used to find the correct rotation-function solution for BLIP. Using the traditional Crowther (1972) fast rotation function, the Z score for the correct BLIP placement is 3.8 and the top Z score of 4.4 corresponds to an incorrect placement. Using MLRF and the prior knowledge about the placement of BETA, the correct placement of BLIP has a Z score of 6.5 and is the highest score in the search. (These results are for data that have had the anisotropy correction applied, to illustrate the improvement given by the MLRF alone.)

Keyword script(s)

MODE MR_AUTO
HKLIN beta_blip.mtz
LABIN F=Fobs SIGF=Sigma
ENSEMBLE BETA PDB beta.pdb ID 100
ENSEMBLE BLIP PDB blip.pdb ID 100
SEARCH ENSEMBLE BETA
SEARCH ENSEMBLE BLIP

Reference(s)

Solving structures of protein complexes by molecular replacement with Phaser

McCoy AJ

Acta Cryst. (2007). D63, 32-41

Figures

File:Beta blip.gif

Structure of the β-lactamase (BETA)–β-lactamase inhibitor (BLIP) complex. BETA is in blue and BLIP is in yellow