Crystal structure of NblA from Anabaena sp. PCC 7120, a small protein playing a key role in phycobilisome degradation

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Item Type:	Article
Title:	Crystal structure of NblA from Anabaena sp. PCC 7120, a small protein playing a key role in phycobilisome degradation
Creators Name:	Bienert, R., Baier, K., Volkmer, R., Lockau, W. and Heinemann, U.
Abstract:	Cyanobacterial light-harvesting complexes, the phycobilisomes, are proteolytically degraded when the organisms are starved for combined nitrogen, a process referred to as chlorosis or bleaching. Gene nblA, present in all phycobilisome-containing organisms, encodes a protein of about 7 kDa that plays a key role in phycobilisome degradation. The mode of action of NblA in this degradation process is poorly understood. Here we presented the 1.8-A crystal structure of NblA from Anabaena sp. PCC 7120. In the crystal, NblA is present as a four-helix bundle formed by dimers, the basic structural units. By using pull-down assays with immobilized NblA and peptide scanning, we showed that NblA specifically binds to the alpha-subunits of phycocyanin and phycoerythrocyanin, the main building blocks of the phycobilisome rod structure. By site-directed mutagenesis, we identified amino acid residues in NblA that are involved in phycobilisome binding. The results provided evidence that NblA is directly involved in phycobilisome degradation, and the results allowed us to present a model that gives insight into the interaction of this small protein with the phycobilisomes.
Keywords:	Amino Acid Sequence, Anabaena, Bacterial Proteins, X-Ray Crystallography, Cyanobacteria, Dimerization, Polyacrylamide Gel Electrophoresis, Bacterial Gene Expression Regulation, Glutathione Transferase, Light-Harvesting Protein Complexes, Molecular Models, Molecular Sequence Data, Site-Directed Mutagenesis, Peptides, Phycobilins, Phycobilisomes, Phycocyanin, Protein Binding, Protein Conformation, Amino Acid Sequence Homology
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	281
Number:	8
Page Range:	5216-5223
Date:	24 February 2006
Official Publication:	https://doi.org/10.1074/jbc.M507243200
PubMed:	View item in PubMed

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