Major constituent of the S-layer. Plays an important role in the structural organization and integrity of the S-layer (PubMed:16946272, PubMed:26074883). 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). Homohexamer; trimer of disulfide-linked dimers. Deletion causes substantial alterations in cell envelope structure, and a significant defect in resistance to solvent and shear stresses. Mutants shed exterior layers of the cellular envelope (PubMed:16946272). Deletion mutants show a significant decrease of the UV resistance, especially under desiccation conditions (PubMed:26909071).