This motif is found at the N terminal of some members of the Peptidase_C1 family (Pfam:PF00112) and is involved in activation of this peptidase [1].

1: Nucleotide and predicted amino acid sequences of cloned human and mouse preprocathepsin B cDNAs. Chan SJ, San Segundo B, McCormick MB, Steiner DF; Proc Natl Acad Sci U S A 1986;83:7721-7725. PMID:3463996