8acq
S-layer Deinoxanthin-Binding Complex (SDBC), subunit DR_2577 assembled with its SOD DR_0644
Structural highlights
FunctionSLPA_DEIRA Plays an important role in the structural organization and integrity of the cell envelope, bridging the outer membrane to the peptidoglyan layer (PubMed:16946272, PubMed:26074883, PubMed:35943982). Is a highly abundant molecule in the D.radiodurans cell envelope but is not a fundamental component of the S-layer (PubMed:35943982). Binds the carotenoid deinoxanthin, a strong protective antioxidant specific of this bacterium, and could be part of the first lane of defense against UV radiation, especially under desiccation (PubMed:26909071). Appears to be a nonselective channel (PubMed:32071085). Is able to transport charged amino acids such as Lys, Arg and Glu; the large dimension of the pore points toward the physiological importance of the SDBC complex in assisting and allowing the exchange of substances, including nutrients, with the surrounding environment (PubMed:35577074).[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedDeinococcus radiodurans is known for its remarkable ability to withstand harsh stressful conditions. The outermost layer of its cell envelope is a proteinaceous coat, the S-layer, essential for resistance to and interactions with the environment. The S-layer Deinoxanthin-binding complex (SDBC), one of the main units of the characteristic multilayered cell envelope of this bacterium, protects against environmental stressors and allows exchanges with the environment. So far, specific regions of this complex, the collar and the stalk, remained unassigned. Here, these regions are resolved by cryo-EM and locally refined. The resulting 3D map shows that the collar region of this multiprotein complex is a trimer of the protein DR_0644, a Cu-only superoxide dismutase (SOD) identified here to be efficient in quenching reactive oxygen species. The same data also showed that the stalk region consists of a coiled coil that extends into the cell envelope for approximately 280 A, reaching the inner membrane. Finally, the orientation and localization of the complex are defined by in situ cryo-electron crystallography. The structural organization of the SDBC couples fundamental UV antenna properties with the presence of a Cu-only SOD, showing here coexisting photoprotective and chemoprotective functions. These features suggests how the SDBC and similar protein complexes, might have played a primary role as evolutive templates for the origin of photoautotrophic processes by combining primary protective needs with more independent energetic strategies. The SDBC is active in quenching oxidative conditions and bridges the cell envelope layers in Deinococcus radiodurans.,Farci D, Graca AT, Iesu L, de Sanctis D, Piano D J Biol Chem. 2023 Jan;299(1):102784. doi: 10.1016/j.jbc.2022.102784. Epub 2022 , Dec 9. PMID:36502921[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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