1i4u

Publication Abstract from PubMed

The previously unknown crystal structure of the C(1) subunit of the carotenoid-binding protein alpha-crustacyanin has been determined using the anomalous scattering available at 1.77 A wavelength to determine the partial structure of the S atoms intrinsic to the native protein. The resulting 'heavy-atom' phases, in conjunction with near-atomic resolution (d(min) = 1.15 A) data, were then used to initiate successful structure determination using a direct-methods approach. This is, to the authors' knowledge, the first time such a small anomalous signal ( approximately 1%) has been used to aid the determination of a macromolecular structure. As well as the structure itself, the methods used during data collection and those used in the elucidation of the sulfur 'heavy-atom' partial structure are described here. As predicted, the C(1) subunit adopts a tertiary structure typical of the lipocalin superfamily: an eight-stranded antiparallel beta-barrel with a repeated +1 topology. The beta-barrel has a calyx shape with the two molecules in the asymmetric unit interacting in such a way that the open ends of each calyx face each other, although they do not form a single elongated pocket. A comparison of this structure with those of other members of the lipocalin superfamily has allowed speculation as to the nature of carotenoid binding by the protein.

The C1 subunit of alpha-crustacyanin: the de novo phasing of the crystal structure of a 40 kDa homodimeric protein using the anomalous scattering from S atoms combined with direct methods.,Gordon EJ, Leonard GA, McSweeney S, Zagalsky PF Acta Crystallogr D Biol Crystallogr. 2001 Sep;57(Pt 9):1230-7. Epub 2001, Aug 23. PMID:11526314^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.