This domain is found at the C-terminal of Type I restriction enzyme HindI endonuclease subunit (also known as R protein) from Haemophilus influenzae related sequences from bacteria and archaea [1]. This domain is typically between 255 to 340 amino acids in length and its function is unknown. This domain is found associated with Pfam:PF04851, Pfam:PF04313.

1: A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes. Roberts RJ, Belfort M, Bestor T, Bhagwat AS, Bickle TA, Bitinaite J, Blumenthal RM, Degtyarev SKh, Dryden DT, Dybvig K, Firman K, Gromova ES, Gumport RI, Halford SE, Hattman S, Heitman J, Hornby DP, Janulaitis A, Jeltsch A, Josephsen J, Kiss A, Klaenhammer TR, Kobayashi I, Kong H, Kruger DH, Lacks S, Marinus MG, Miyahara M, Morgan RD, Murray NE, Nagaraja V, Piekarowicz A, Pingoud A, Raleigh E, Rao DN, Reich N, Repin VE, Selker EU, Shaw PC, Stein DC, Stoddard BL, Szybalski W, Trautner TA, Van Etten JL, Vitor JM, Wilson GG, Xu SY; Nucleic Acids Res. 2003;31:1805-1812. PMID:12654995