This is a receiver domain (REC) commonly found in the same gene-neighbourhood of its cognate HK. Together they comprise a Two-Component System (TCS). There is a high degree of specificity among REC and DHp domains in a cognate pair. This domain is related to the Response_reg (Pfam:PF00072) domain. We found that Pfam:PF19191 and this domain show high degree of linkage in the same gene-neighbourhoods across several bacterial lineages. This implies that they comprise a TCS [3].

1: Biological insights from structures of two-component proteins. Gao R, Stock AM; Annu Rev Microbiol. 2009;63:133-154. PMID:19575571

2: The mechanism of signal transduction by two-component systems. Casino P, Rubio V, Marina A; Curr Opin Struct Biol. 2010;20:763-771. PMID:20951027

3: Novel Two-Component System-Like Elements Reveal Functional Domains Associated with Restriction-Modification Systems and paraMORC ATPases in Bacteria. Bellieny-Rabelo D, Pretorius WJS, Moleleki LN; Genome Biol Evol. 2021; [Epub ahead of print] PMID:33565597