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

Hackenberg, Claudia, Hakanpaeae, Johanna, Cai, Fei, Antonyuk, Svetlana ORCID: 0000-0002-2779-9946, Eigner, Caroline, Meissner, Sven, Laitaoja, Mikko, Janis, Janne, Kerfeld, Cheryl A, Dittmann, Elke
et al (show 1 more authors) (2018) Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 115 (27). pp. 7141-7146.

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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 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 <i>Microcystis aeruginosa</i> 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.

Item Type: Article
Uncontrolled Keywords: crystal structure, hexamer, redox, Microcystis aeruginosa
Depositing User: Symplectic Admin
Date Deposited: 06 Jul 2018 11:36
Last Modified: 19 Jan 2023 01:31
DOI: 10.1073/pnas.1806668115
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