This domain family is found in bacteria, and is approximately 40 amino acids in length. This family is a Rickettsia surface antigen of 120 KDa which may be used as an antigen for immune response against the bacterial species.

1: Cloning, sequencing, and expression of the gene coding for an antigenic 120-kilodalton protein of Rickettsia conorii. Schuenke KW, Walker DH; Infect Immun. 1994;62:904-909. PMID:8112862