This is a periplasmic sensor domain found at the N-terminal of c-di-GMP phosphodiesterases, which is a variation of the CSS motif sensor Pfam:PF12792 [1]. This domain, apart of the CSS motif, has an additional conserved CxxC motif, which presumably broaden its redox-sensing palette. It has been found in Shewanella spp. and other members of Altermonadales, Vibrionales and in some acidobacteria [1].

1: Comparative Genomics of Cyclic di-GMP Metabolism and Chemosensory Pathways in Shewanella algae Strains: Novel Bacterial Sensory Domains and Functional Insights into Lifestyle Regulation. Martin-Rodriguez AJ, Higdon SM, Thorell K, Tellgren-Roth C, Sjoling A, Galperin MY, Krell T, Romling U; mSystems. 2022; [Epub ahead of print] PMID:35311563