4po5

Crystal structure of allophycocyanin B from Synechocystis PCC 6803

spinqualitylabelsall models 4po5, resolution 1.75Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4po5 is a 6 chain structure with sequence from Synechocystis sp.. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CYC, SO4 NonStd Res: MEN Resources: FirstGlance, OCA, RCSB, PDBsum Function [PHAC_SYNY3] Light-harvesting photosynthetic bile pigment-protein from the phycobiliprotein complex. Allophycocyanin has a maximum absorption at approximately 654 nanometers (By similarity). [PHAB_SYNY3] Light-harvesting photosynthetic bile pigment-protein from the phycobiliprotein complex. Allophycocyanin has a maximum absorption at approximately 650 nanometers. Publication Abstract from PubMed Allophycocyanin B (AP-B) is one of the two terminal emitters in phycobilisomes, the unique light-harvesting complexes of cyanobacteria and red algae. Its low excitation-energy level and the correspondingly redshifted absorption and fluorescence emission play an important role in funnelling excitation energy from the hundreds of chromophores of the extramembraneous phycobilisome to the reaction centres within the photosynthetic membrane. In the absence of crystal structures of these low-abundance terminal emitters, the molecular basis for the extreme redshift and directional energy transfer is largely unknown. Here, the crystal structure of trimeric AP-B [(ApcD/ApcB)3] from Synechocystis sp. PCC 6803 at 1.75 A resolution is reported. In the crystal lattice, eight trimers of AP-B form a porous, spherical, 48-subunit assembly of 193 A in diameter with an internal cavity of 1.1 x 10(6) A(3). While the overall structure of trimeric AP-B is similar to those reported for many other phycobiliprotein trimers, the chromophore pocket of the alpha-subunit, ApcD, has more bulky residues that tightly pack the phycocyanobilin (PCB). Ring D of the chromophores is further stabilized by close interactions with ApcB from the adjacent monomer. The combined contributions from both subunits render the conjugated rings B, C and D of the PCB in ApcD almost perfectly coplanar. Together with mutagenesis data, it is proposed that the enhanced planarity effectively extends the conjugation system of PCB and leads to the redshifted absorption (lambdamax = 669 nm) and fluorescence emission (679 nm) of the ApcD chromophore in AP-B, thereby enabling highly efficient energy transfer from the phycobilisome core to the reaction centres. The structure of allophycocyanin B from Synechocystis PCC 6803 reveals the structural basis for the extreme redshift of the terminal emitter in phycobilisomes.,Peng PP, Dong LL, Sun YF, Zeng XL, Ding WL, Scheer H, Yang X, Zhao KH Acta Crystallogr D Biol Crystallogr. 2014 Oct 1;70(Pt 10):2558-69. doi:, 10.1107/S1399004714015776. Epub 2014 Sep 27. PMID:25286841 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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