This is the E+ motif found in some plant pentatricopeptide repeat (PPR) proteins [1,2] which contain a C-terminal DYW deaminase domain. The DYW domain is required for RNA editing, a process that deaminates specific cytidines to uridines. This motif, together with the E motif, precedes the DYW domain and, although their role is not clear, they are essential in th RNA editing reaction [1,2]. The E/E+ motifs may contain two degenerate PPR motifs that could be involved in RNA or protein binding.

1: Cytidine deaminase motifs within the DYW domain of two pentatricopeptide repeat-containing proteins are required for site-specific chloroplast RNA editing. Wagoner JA, Sun T, Lin L, Hanson MR; J Biol Chem. 2015;290:2957-2968. PMID:25512379

2: MEF10 is required for RNA editing at nad2-842 in mitochondria of Arabidopsis thaliana and interacts with MORF8. Hartel B, Zehrmann A, Verbitskiy D, van der Merwe JA, Brennicke A, Takenaka M; Plant Mol Biol. 2013;81:337-346. PMID:23288601