标题：Evolution of a light-harvesting protein by addition of new subunits and rearrangement of conserved elements: Crystal structure of a cryptophyte phycoerythrin at 1.63-Å resolution
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：16
页码：8901-8906
DOI：10.1073/pnas.96.16.8901
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Cryptophytes are unicellular photosynthetic algae that use a lumenally located light-harvesting system, which is distinct from the phycobilisome structure found in cyanobacteria and red algae. One of the key components of this system is water-soluble phycoerythrin (PE) 545 whose expression is enhanced by low light levels. The crystal structure of the heterodimeric 12{beta}{beta} PE 545 from the marine cryptophyte Rhodomonas CS24 has been determined at 1.63-A resolution. Although the {beta}-chain structure is similar to the and {beta} chains of other known phycobiliproteins, the overall structure of PE 545 is novel with the chains forming a simple extended fold with an antiparallel {beta}-ribbon followed by an -helix. The two doubly linked {beta}50/{beta}61 chromophores (one on each {beta} subunit) are in van der Waals contact, suggesting that exciton-coupling mechanisms may alter their spectral properties. Each subunit carries a covalently linked 15,16-dihydrobiliverdin chromophore that is likely to be the final energy acceptor. The architecture of the heterodimer suggests that PE 545 may dock to an acceptor protein via a deep cleft and that energy may be transferred via this intermediary protein to the reaction center.
