This family named after a PE motif near to the amino terminus of the domain. The PE family of proteins all contain an amino-terminal region of about 110 amino acids. The carboxyl terminus of this family are variable and fall into several classes. The largest class of PE proteins is the highly repetitive PGRS class which have a high glycine content. The function of these proteins is uncertain but it has been suggested that they may be related to antigenic variation of Mycobacterium tuberculosis [1]. The C-terminus of this domain contains the type VII secretion signal that has a YXXXD/E motif.

1: Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence. Cole ST, Brosch R, Parkhill J, Garnier T, Churcher C, Harris D, Gordon SV, Eiglmeier K, Gas S, Barry CE 3rd, Tekaia F, Badcock K, Basham D, Brown D, Chillingworth T, Connor R, Davies R, Devlin K, Feltwell T, Gentles S, Hamlin N, Holroyd S, Hornsby T, Jage Nature 1998;393:537-544. PMID:9634230

2: Toward the structural genomics of complexes: crystal structure of a PE/PPE protein complex from Mycobacterium tuberculosis. Strong M, Sawaya MR, Wang S, Phillips M, Cascio D, Eisenberg D; Proc Natl Acad Sci U S A. 2006;103:8060-8065. PMID:16690741