期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 115, 期 27, 页码 7141-7146出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1806668115
关键词
crystal structure; hexamer; redox; Microcystis aeruginosa
资金
- EMBL
- US Department of Energy, Basic Energy Sciences [DE-FG02-91ER20021]
- National Science Foundation [IOS 1557324]
- German Research Foundation (DFG) [Di910/10-1]
- Erasmus scholarship
- r Finland/Biocenter Kuopio
- European Union Regional Fund [A70135]
- European Union's Horizon 2020 research and innovation program [731077]
Cyanobacteria are important photosynthetic organisms inhabiting a range of dynamic environments. This phylum is distinctive among photosynthetic organisms in containing genes encoding uncharacterized cystathionine beta-synthase (CBS)-chloroplast protein (CP12) fusion proteins. These consist of two domains, each recognized as stand-alone photosynthetic regulators with different functions described in cyanobacteria (CP12) and plants (CP12 and CBSX). Here we show that CBS-CP12 fusion proteins are encoded in distinct gene neighborhoods, several unrelated to photosynthesis. Most frequently, CBS-CP12 genes are in a gene cluster with thioredoxin A (TrxA), which is prevalent in bloom-forming, marine symbiotic, and benthic mat cyanobacteria. Focusing on a CBS-CP12 from Microcystis aeruginosa PCC 7806 encoded in a gene cluster with TrxA, we reveal that the domain fusion led to the formation of a hexameric protein. We show that the CP12 domain is essential for hexamerization and contains an ordered, previously structurally uncharacterized N-terminal region. We provide evidence that CBS-CP12, while combining properties of both regulatory domains, behaves different from CP12 and plant CBSX. It does not form a ternary complex with phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase. Instead, CBS-CP12 decreases the activity of PRK in an AMP-dependent manner. We propose that the novel domain architecture and oligomeric state of CBS-CP12 expand its regulatory function beyond those of CP12 in cyanobacteria.
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