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Structure of lobster apocrustacyanin A1 using softer X-rays.
M Cianci1, P J Rizkallah, A Olczak
1Department of Chemistry, University of Manchester, Manchester M13 9PL, England.
Acta Crystallographica. Section D, Biological Crystallography
|August 30, 2001
Summary
The crystal structure of the A(1) protein, a subunit of lobster crustacyanin, was solved using soft X-rays. This provides a model for understanding blue coloration in marine crustaceans and astaxanthin binding.
Area of Science:
- Structural Biology
- Biochemistry
- Marine Biology
Background:
- Marine crustacean coloration, like the blue of lobster carapace, is often due to carotenoproteins.
- Crustacyanin, a key protein, exists as a 16-mer complex with astaxanthin, composed of CRTC and CRTA subfamilies.
Purpose of the Study:
- To solve the crystal structure of the A(1) protein from the CRTC subfamily of crustacyanin.
- To develop new methods for overcoming challenges in CRTC protein structure determination.
Main Methods:
- Utilized soft X-rays (2 Å wavelength) and a xenon derivative for structure solution.
- Employed SIROAS phasing with xenon and sulfur anomalous signals from native data sets.
- Refined the structure using a high-resolution, short-wavelength data set, all collected at 100 K.
Main Results:
- Determined the crystal structure of the A(1) CRTC protein dimer to 1.4 Å resolution.
- The structure revealed a typical lipocalin fold, closely resembling insecticyanin and retinol-binding protein.
- Achieved R factor of 17.7% and R(free) of 22.9%.
Conclusions:
- The solved A(1) structure serves as a crucial model for studying astaxanthin binding in crustacyanins.
- This structural information aids in understanding the molecular basis of camouflage coloration in marine crustaceans.