This family matches additional variants of the PPR repeat that were not captured by the model for Pfam:PF01535. In the case of the Arabidopsis protein UniProtKB:Q66GI4, the repeated helices in this N-terminal region, of protein-only RNase P (PRORP) enzymes, form the pentatricopeptide repeat (PPR) domain which enhances pre-tRNA binding affinity. PROPRP enzymes process precursor tRNAs in human mitochondria and in all tRNA-using compartments of Arabidopsis thaliana [1].

1: Mitochondrial ribonuclease P structure provides insight into the evolution of catalytic strategies for precursor-tRNA 5' processing. Howard MJ, Lim WH, Fierke CA, Koutmos M; Proc Natl Acad Sci U S A. 2012;109:16149-16154. PMID:22991464