Structural analysis at 2.2 A of orthorhombic crystals presents the asymmetry of the allophycocyanin-linker complex, AP.LC7.8, from phycobilisomes of Mastigocladus laminosus.
An electrophoretically purified allophycocyanin-linker complex, AP. LC7.8, from phycobilisomes of Mastigocladus laminosus has been crystallized in the orthorhombic space group P212121. Cryocrystallographic x-ray measurements enabled the structural analysis of the complex at a resolution of 2.2 A. The asymmetric unit contains two side-to-side associated "trimeric" (alphabeta)3 allophycocyanin complexes comprising the linker polypeptide in a defined orientation inside the trimer. The linker representing a protein fold related to the prosegment of procarboxypeptidase A is in contact with only two of the three beta-subunits and directly interacts with the corresponding chromophores of these proteins. In addition to a modulation of the chromophores' spectral properties, the linker polypeptide attracts the alphabeta-subcomplexes, thereby bringing the beta-chromophores closer together. These results will enable interpretations of energy-transfer mechanisms within phycobiliproteins.
Reuter
W
W
Max-Planck-Institut für Biochemie, Am Klopferspitz 18A, D-82158 Martinsried, Germany.
Wiegand
G
G
Huber
R
R
Than
M E
ME
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000378:metabolism*; D005583:Fourier Analysis; D045342:Light-Harvesting Protein Complexes; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D045524:Phycobilisomes; D010798:Phycocyanin / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary