The Role of Iron and Copper on the Oligomerization Dynamics of DR_2577, the Main S-Layer Protein of Deinococcus radiodurans

Abstract

Surface (S)-layers are cryptic structures that coat the external surface of the bacterial cell in many species. The paracrystalline regularity of the S-layer is due to the self-assembling of one or more protein units. The property of self-assembling seems to be mediated by specific topologies of the S-layer proteins as well as the presence of specific ions that provide support in building and stabilizing the bi-dimensional S-layer organization. In the present study, we have investigated the self-assembling mechanism of the main S-layer protein of Deinococcus radiodurans (DR_2577) finding an unusual role played by Fe 3+ and Cu 2+ in the oligomerization of this protein. These findings may trace a structural and functional metallo-mediated convergence between the role of these metals in the assembling of the S-layer and their well-known roles in protecting against oxidative stress in D. radiodurans .

The cryo-EM structure of the S-layer deinoxanthin-binding complex of Deinococcus radiodurans informs properties of its environmental interactions

“…The SDBC is known to retain metal ions ( 16 ), and in the present report four metal-binding sites were identified and assigned to Cu and Fe ( Fig. 2 ).…”

“…S2 and Table S1 ). The presence of these sites might be important for stabilizing the complex as previously reported ( 16 ).

Figure 2 Metal-binding sites of the SDBC.

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“…The main component of this S-layer is the protein DR_2577 (SlpA), which binds the xanthophyll carotenoid deinoxanthin and was found to be part of a hetero-oligomeric complex resulting in the main assembly named S-layer deinoxanthin-binding complex (SDBC). The SDBC was extensively characterized both functionally and biochemically providing important information with respect to its stability, oligomerization, and spectral properties ( 13 , 14 , 15 , 16 , 17 ). In addition to DR_2577, this complex was found to be composed of other five different subunits, namely DR_2310, DR_0505, DR_A0283, DR_A0282, and DR_A0281 ( 18 ).…”

Mesoscale organization in the cell envelope of Deinococcus radiodurans

“…3a). According to the p6 symmetry of this S-layer, each T4P-like is surrounded by 6 copies of a smaller complex, the S-layer Deinoxanthin Binding Complex (SDBC), extensively described and characteristic of these cell envelopes (Farci et al , 2016; Farci et al , 2019; Farci et al , 2020; Farci et al , 2021). Recognizable by its triangular shape (with a side length of 90 Å and a thickness of ~30 Å), this ~0.9 MDa complex has the main body embedded in the outer membrane and is located inside of a “cell envelope case” (Fig.…”

Structural analysis of the architecture and in situ localization of the main S-layer complex in Deinococcus radiodurans

“…These studies identified a dozen proteins involved in the articulated paracrystalline order of the S-layer (Farci et al, 2014) and allocated them into at least two specific hetero-oligomeric complexes, the S-layer deinoxanthin-binding complex (SDBC), accounting for the interpore region of this S-layer (Farci et al, 2016), and a type IV-like piliation system, accounting for the pore region (Farci et al, 2014). Among these complexes, the main one, the SDBC, was broadly characterized both functionally and biochemically (Farci et al, 2015(Farci et al, , 2016(Farci et al, , 2018(Farci et al, , 2019Rothfuss et al, 2006;Ott et al, 2019aOtt et al, , 2019bLim et al, 2019;Adamec et al, 2020), but only recently have some of its structural features been disclosed (Farci et al, 2020).…”