1x0p

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Structure of a cyanobacterial BLUF protein, Tll0078

Overview

The sensor proteins for blue light using the FAD (BLUF) domain belong to, the third family of the photoreceptor proteins using a flavin chromophore, where the other two families are phototropins and cryptochromes. As the, first structure of this BLUF domain, we have determined the crystal, structure of the Tll0078 protein from Thermosynechococcus elongatus BP-1, which contains a BLUF domain bound to FAD, at 2A resolution. Five Tll0078, monomers are located around the non-crystallographic 5-fold axis to form a, pentamer, and two pentamers related by 2-fold non-crystallographic, symmetry form a decameric assembly. The monomer consists of two domains, the BLUF domain at the N-terminal region and the C-terminal domain. The, overall structure of the BLUF domain consists of a five-stranded mixed, beta-sheet with two alpha-helices running parallel with it. The, isoalloxazine ring of FAD is accommodated in a pocket formed by several, highly conserved amino acid residues in the BLUF domain. Of these, the, three apparent key residues (Asn31, Asn32 and Gln50) were substituted with, Ala. Mutant proteins of N31A and N32A showed a nearly normal 10nm spectral, shift of the flavin upon illumination, while the Q50A mutant did not, exhibit such a shift at all. On the basis of the crystal structure, we, discussed a possible role of Gln50, which is structurally and functionally, linked with the critical Tyr8 (FAD-Gln50-Tyr8 network), with regard to the, light-induced spectral shift of the BLUF proteins.

About this Structure

1X0P is a Single protein structure of sequence from Thermosynechococcus elongatus with FAD as ligand. Full crystallographic information is available from OCA.

Reference

Structure of a cyanobacterial BLUF protein, Tll0078, containing a novel FAD-binding blue light sensor domain., Kita A, Okajima K, Morimoto Y, Ikeuchi M, Miki K, J Mol Biol. 2005 May 27;349(1):1-9. Epub 2005 Apr 9. PMID:15876364

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