MASE4 (Membrane-Associated SEnsor) is an integral membrane sensor domain found in various GGDEF domain proteins, including a functional diguanylate cyclase DgcT (YcdT) and the enzymatically inactive CdgI (YeaI) of Escherichia coli [1]. In the Shiga toxin-producing enteroaggregative E. coli O104:H4, which caused the outbreak of the haemolytic uraemic syndrome in Germany in 2011, MASE4-containing diguanylate cyclase DgcX, UniProtKB:B7LBD9_ECO55, was highly expressed, ensuring strong biofilm formation [2].

1: Systematic Nomenclature for GGDEF and EAL Domain-Containing Cyclic Di-GMP Turnover Proteins of Escherichia coli. Hengge R, Galperin MY, Ghigo JM, Gomelsky M, Green J, Hughes KT, Jenal U, Landini P; J Bacteriol. 2015;198:7-11. PMID:26148715

2: Cyclic-di-GMP signalling and biofilm-related properties of the Shiga toxin-producing 2011 German outbreak Escherichia coli O104:H4. Richter AM, Povolotsky TL, Wieler LH, Hengge R; EMBO Mol Med. 2014;6:1622-1637. PMID:25361688