Gao, Xiang; Zhang, Nan; Wei, Tian-Di; Su, Hai-Nan; Xie, Bin-Bin; Dong, Chuang-Chuang; Zhang, Xi-Ying; Chen, Xiu-Lan; Zhou, Bai-Cheng; Wang, Zhi-Xin; Wu, Jia-Wei; Zhang, Yu-Zhong
Crystal structure of the N-terminal domain of linker L-R and the assembly of cyanobacterial phycobilisome rods
MOLECULAR MICROBIOLOGY, 82:698-705, NOV 2011

Phycobilisomes are light-harvesting supramolecular complexes in cyanobacteria and red algae. Linkers play a pivotal role in the assembly and energy transfer modulation of phycobilisomes. However, how linkers function remains unclear due to the lack of structural and biochemical studies of linkers, especially the N-terminal domain of LR (pfam00427). Here, we report the crystal structure of the pfam00427 domain of the linker L-R(30) from Synechocystis sp. PCC 6803 at 1.9 angstrom. The pfam00427 presents as a previously uncharacterized point symmetric six alpha-helix bundle. To elucidate the binding style of pfam00427 in the C-phycocyanin (C-PC) (alpha beta)(6) hexamer, we fixed pfam00427 computationally into the C-PC (alpha beta)(6) inner cavity using the program AutoDock. Combined with a conserved 'C-PC binding patch' on pfam00427 identified, we arrived at a model for the pfam00427-C-PC (alpha beta)(6) complex. This model was further optimized and evaluated as a reasonable result by a molecular dynamics simulation. In the resulting model, the pfam00427 domain is stably positioned in the central hole of the C-PC trimer. Moreover, the L-RT (pfam01383) was docked into our pfam00427-C-PC model to generate a complete phycobilisome rod in which the linkers join individual biliprotein hexamers.

DOI:10.1111/j.1365-2958.2011.07844.x

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