Publication Date:
2015-07-28
Description:
The crystallographic analysis of a marine cyanobacterium (Phormidiumsp. A09DM) phycoerythrin (PE) that shows distinct sequence features compared with known PE structures from cyanobacteria and red algae is reported.PhormidiumPE was crystallized using the sitting-drop vapour-diffusion method with ammonium sulfate as a precipitant. Diffraction data were collected on the protein crystallography beamline at the Indus-2 synchrotron. The crystals diffracted to about 2.1 Å resolution at 100 K. The crystals, with an apparent hexagonal morphology, belonged to space groupP1, with unit-cell parametersa= 108.3,b= 108.4 Å,c= 116.6 Å, α = 78.94, β = 82.50, γ = 60.34°. The molecular-replacement solution confirmed the presence of 12 αβ monomers in theP1 cell. ThePhormidiumPE elutes as an (αβ)3trimer of αβ monomers from a molecular-sieve column and exists as [(αβ)3]2hexamers in the crystal lattice. Unlike red algal PE proteins, the hexamers ofPhormidiumPE do not form higher-order structures in the crystals. The existence of only one characteristic visual absorption band at 564 nm suggests the presence of phycoerythrobilin chromophores, and the absence of any other types of bilins, in thePhormidiumPE assembly.
Electronic ISSN:
2053-230X
Topics:
Biology
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Chemistry and Pharmacology
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Geosciences
,
Physics
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