This entry represents the membrane-associated sensor domain 9 (MASE9), which has been found in combination with HD-GYP and GGDEF-EAL domains , or in MASE9-HD-GYP-GAF-GGDEF domain architecture [1]. It has 8 predicted transmembrane (TM) segments of which two are likely to form an intramembrane hairpin. It has several charged residues in the hydrophobic core of the membrane, that, in addition to the poor conservation of the short periplasmic segments, suggests that ligand binding and/or protein-protein interactions by MASE9 may occur within the membrane [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