This domain is found in several cell surface proteins, such as extracellular matrix-binding protein ebh [1]. Some members are involved in antibiotic resistance (e.g Swiss:Q9RL69 and Swiss:Q9LCJ9) [2] and/or cellular adhesion (e.g. Swiss:Q931R6) [1]. In some proteins it is repeated more than fifteen times, being the most repeated domain in streptococci [3]. This is a predominantly alpha-helical domain that form a long, thin, fibre-like structure and it has been proposed to function as a stalk that helps the adhesive non-repeat region (NRR) of proteins protrude beyond the cell surface [4,5].

1: Analysis of Ebh, a 1.1-megadalton cell wall-associated fibronectin-binding protein of Staphylococcus aureus. Clarke SR, Harris LG, Richards RG, Foster SJ; Infect Immun 2002;70:6680-6687. PMID:12438342

2: Mrp--a new auxiliary gene essential for optimal expression of methicillin resistance in Staphylococcus aureus. Wu SW, De Lencastre H; Microb Drug Resist 1999;5:9-18. PMID:10332717

3: Protein domain repetition is enriched in Streptococcal cell-surface proteins. Lin IH, Hsu MT, Chang CH; Genomics. 2012;100:370-379. PMID:22921469

4: A novel sialic acid-binding adhesin present in multiple species contributes to the pathogenesis of Infective endocarditis. Gaytan MO, Singh AK, Woodiga SA, Patel SA, An SS, Vera-Ponce de Leon A, McGrath S, Miller AR, Bush JM, van der Linden M, Magrini V, Wilson RK, Kitten T, King SJ; PLoS Pathog. 2021;17:e1009222. PMID:33465168

5: The extracellular protein factor Epf from Streptococcus pyogenes is a cell surface adhesin that binds to cells through an N-terminal domain containing a carbohydrate-binding module. Linke C, Siemens N, Oehmcke S, Radjainia M, Law RH, Whisstock JC, Baker EN, Kreikemeyer B; J Biol Chem. 2012;287:38178-38189. PMID:22977243