1h91
From Proteopedia
| |||||||
| , resolution 1.40Å | |||||||
|---|---|---|---|---|---|---|---|
| Sites: | , , and | ||||||
| Ligands: | |||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
THE CRYSTAL STRUCTURE OF LOBSTER APOCRUSTACYANIN A1 USING SOFTER X-RAYS.
Overview
The molecular basis of the camouflage colouration of marine crustacea is often provided by carotenoproteins. The blue colour of the lobster carapace, for example, is intricately associated with a multimacromolecular 16-mer complex of protein subunits each with a bound astaxanthin molecule. The protein subunits of crustacyanin fall into two distinct subfamilies, CRTC and CRTA. Here, the crystal structure solution of the A(1) protein of the CRTC subfamily is reported. The problematic nature of the structure solution of the CRTC proteins (both C(1) and A(1)) warranted consideration and the development of new approaches. Three putative disulfides per protein subunit were likely to exist based on molecular-homology modelling against known lipocalin protein structures. With two such subunits per crystallographic asymmetric unit, this direct approach was still difficult as it involved detecting a weak signal from these sulfurs and suggested the use of softer X-rays, combined with high data multiplicity, as reported previously [Chayen et al. (2000), Acta Cryst. D56, 1064-1066]. This paper now describes the structure solution of CRTC in the form of the A(1) dimer based on use of softer X-rays (2 A wavelength). The structure solution involved a xenon derivative with an optimized xenon L(I) edge f" signal and a native data set. The hand of the xenon SIROAS phases was determined by using the sulfur anomalous signal from a high-multiplicity native data set also recorded at 2 A wavelength. For refinement, a high-resolution data set was measured at short wavelength. All four data sets were collected at 100 K. The refined structure to 1.4 A resolution based on 60 276 reflections has an R factor of 17.7% and an R(free) of 22.9% (3137 reflections). The structure is that of a typical lipocalin, being closely related to insecticyanin, to bilin-binding protein and to retinol-binding protein. This A(1) monomer or dimer can now be used as a search motif in the structural studies of the oligomeric forms alpha- and beta-crustacyanins, which contain bound astaxanthin molecules.
About this Structure
1H91 is a Single protein structure of sequence from Homarus gammarus. Full crystallographic information is available from OCA.
Reference
Structure of lobster apocrustacyanin A1 using softer X-rays., Cianci M, Rizkallah PJ, Olczak A, Raftery J, Chayen NE, Zagalsky PF, Helliwell JR, Acta Crystallogr D Biol Crystallogr. 2001 Sep;57(Pt 9):1219-29. Epub 2001, Aug 23. PMID:11526313
Page seeded by OCA on Thu Mar 20 11:33:55 2008
