This family, which was previously known as DUF860, has been shown to be a component of group II intron ribonucleoprotein particles in maize chloroplasts. The domain is required for the splicing of the introns with which it associates, and promotes splicing in the context of a heterodimer with the RNase III-domain protein RNC1. All of the members are predicted to localise to mitochondria or chloroplasts [1]. It seems likely that most PORR proteins function in organellar RNA metabolism [2].

1: A plant-specific RNA-binding domain revealed through analysis of chloroplast group II intron splicing. Kroeger TS, Watkins KP, Friso G, van Wijk KJ, Barkan A; Proc Natl Acad Sci U S A. 2009;106:4537-4542. PMID:19251672

2: A novel plant-specific family gene, ROOT PRIMORDIUM DEFECTIVE 1, is required for the maintenance of active cell proliferation. Konishi M, Sugiyama M; Plant Physiol. 2006;140:591-602. PMID:16407439