1ksa

From Proteopedia

CRYSTAL STRUCTURE OF THE BACTERIOCHLOROPHYLL A PROTEIN FROM CHLOROBIUM TEPIDUM

Overview

The bacteriochlorophyll (BChl) a protein from Chlorobium tepidum, which, participates in energy transfer in green photosynthetic bacteria, has been, crystallized using the sitting drop method of vapor diffusion. X-ray, diffraction data collected from these crystals indicate that the crystals, belong to the cubic space group P4132 with cell dimensions of a=b=c=169.5, A. A native X-ray diffraction data set has been collected to a resolution, of 2.2 A. The initial solution was determined by using the molecular, replacement method using the structure of the previously solved BChl a, protein from Prosthecochloris aestuarii. A unique rotation and translation, solution was obtained for two monomers in the asymmetric unit giving a, pseudo-body centered packing. After rebuilding and refinement the model, yields an R factor of 19.0%, a free R-factor of 28.3%, and good geometry, with root-mean-square deviations of 0.013 A and 2.1 degrees for the bond, lengths and angles, respectively. The structure of the BChl a protein from, C. tepidum consists of three identical subunits related by a 3-fold axis, of crystallographic symmetry. In each subunit the polypeptide backbone, forms large beta-sheets and encloses a central core of seven BChl a, molecules. The distances between neighboring bacteriochlorin systems, within a subunit range between 4 A to 11 A and that between two, bacteriochlorins from different subunits is more than 20 A. The overall, structure is comparable with that of P. aestuarii but significant, differences are observed for the individual bacteriochlorophyll, structures. The surface of the trimer has a hydrophobic region that is, modeled as the complex being a peripheral membrane protein partially, embedded in the membrane. A general model is presented for the membrane, organization with two of the bacteriochlorophyll structures in the, membrane and transferring energy to the reaction center complex. In this, model these two bacteriochlorophyll structures serve a similar role to the, cofactors of integral membrane light-harvesting complexes although the, protein structure surrounding the cofactors is significantly different for, the BChl a protein compared with the integral membrane complexes.

About this Structure

1KSA is a Single protein structure of sequence from Chlorobaculum tepidum with BCL as ligand. Full crystallographic information is available from OCA.

Reference

Crystal structure of the bacteriochlorophyll a protein from Chlorobium tepidum., Li YF, Zhou W, Blankenship RE, Allen JP, J Mol Biol. 1997 Aug 22;271(3):456-71. PMID:9268671

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