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Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria.

ABSTRACT: Cyanobacteria are important photosynthetic organisms inhabiting a range of dynamic environments. This phylum is distinctive among photosynthetic organisms in containing genes encoding uncharacterized cystathionine ?-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.

SUBMITTER: Hackenberg C

PROVIDER: S-EPMC6142219 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria.

Hackenberg Claudia C Hakanpää Johanna J Cai Fei F Antonyuk Svetlana S Eigner Caroline C Meissner Sven S Laitaoja Mikko M Jänis Janne J Kerfeld Cheryl A CA Dittmann Elke E Lamzin Victor S VS

Proceedings of the National Academy of Sciences of the United States of America 20180618 27

Cyanobacteria are important photosynthetic organisms inhabiting a range of dynamic environments. This phylum is distinctive among photosynthetic organisms in containing genes encoding uncharacterized cystathionine β-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 enco ...[more]

PMID: 29915055

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Dataset Information

Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria.

Publications

Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria.

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