期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 288, 期 22, 页码 16055-16063出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M113.456897
关键词
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资金
- National Science Foundation [MCB0851094, EF1105897]
- Swiss National Science Foundation
- Office of Science, Office of Basic Energy Sciences, of the United States Department of Energy [DE-AC02-05CH11231]
The carboxysome is a bacterial organelle found in all cyanobacteria; it encapsulates CO2 fixation enzymes within a protein shell. The most abundant carboxysome shell protein contains a single bacterial microcompartment (BMC) domain. We present in vivo evidence that a hypothetical protein (dubbed CcmP) encoded in all beta-cyanobacterial genomes is part of the carboxysome. We show that CcmP is a tandem BMC domain protein, the first to be structurally characterized from a beta-carboxysome. CcmP forms a dimer of tightly stacked trimers, resulting in a nanocompartment-containing shell protein that may weakly bind 3-phosphoglycerate, the product of CO2 fixation. The trimers have a large central pore through which metabolites presumably pass into the carboxysome. Conserved residues surrounding the pore have alternate side-chain conformations suggesting that it can be open or closed. Furthermore, CcmP and its orthologs in alpha-cyanobacterial genomes form a distinct clade of shell proteins. Members of this subgroup are also found in numerous heterotrophic BMC-associated gene clusters encoding functionally diverse bacterial organelles, suggesting that the potential to form a nanocompartment within a microcompartment shell is widespread. Given that carboxysomes and architecturally related bacterial organelles are the subject of intense interest for applications in synthetic biology/metabolic engineering, our results describe a new type of building block with which to functionalize BMC shells.
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