This is the membrane-associated sensor domain 12 (MASE12), found in (predicted) c-di-GMP phosphodiesterases and histidine kinases [1]. This domain has conserved aromatic residues in the transmembrane segments, which suggests that its ligand could be a molecule with one or more aromatic rings [1].

1: Sequence Conservation, Domain Architectures, and Phylogenetic Distribution of the HD-GYP Type c-di-GMP Phosphodiesterases. Galperin MY, Chou SH; J Bacteriol. 2021; [Epub ahead of print] PMID:34928179