This is the membrane-associated sensor domain 10 (MASE10) which has conserved Cys, Ser and Trp residues in the periplasmic loop, conserved aromatic residues and four charged (Arg, Asp, Lys, and another Asp) residues in the predicted transmembrane segments, suggesting specific interaction with its small molecule or protein ligands [1]. It has been found in c-di-GMP phosphodiesterases, adenylate/guanylate cyclases and Ser/Thr protein phosphatases of the PP2C family, in which MASE10 is followed by the signal-transducing HAMP domain [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