Structural insights into the main S-layer unit of Deinococcus radiodurans reveal a massive protein complex with porin-like features
Domenica Farci, M. Alphan Aksoyoglu, Stefano Francesco Farci, Jayesh Arun Bafna, Igor Bodrenko, Matteo Ceccarelli, Joanna Kirkpatrick, Mathias Winterhalter, Sami Kereı̈che, Dario Piano
Abstract
-dodecyl-β-d-maltoside, which preserved both hydrophilic and hydrophobic components of the SDBC and allows the retention of several minor subunits. As observed by low-resolution single-particle analysis, we show that the complex possesses a porin-like structural organization, but is larger than other known porins. We also noted that the main SDBC component, the protein DR_2577, shares regions of similarity with known porins. Moreover, results from electrophysiological assays with membrane-reconstituted SDBC disclosed that it is a nonselective channel that has some peculiar gating properties, but also exhibits behavior typically observed in pore-forming proteins, such as porins and ionic transporters. The functional properties of this system and its porin-like organization provide information critical for understanding ion permeability through the outer cell surface of S-layer-carrying bacterial species.