The Nature and Arrangement of Pentatricopeptide Domains and theLinker Sequences Between Them

摘要

The tricopeptide (amino acid number in the 30s) repeats constitute some of themost common amino acid repeats in proteins of diverse organisms. The mostimportant representatives of this class are the 34-residue and 35-residuerepeats, eponymously known as tetratricopeptide repeat (TPR) andpentatricopeptide repeat (PPR), respectively. The unit motif of both consists ofa pair of alpha helices. As members of the large, all-helical repeat classes,TPR and PPR share structural similarities, but also play specific roles inprotein function. In this study, a comprehensive bioinformatic analysis of thePPR units and the linkers that connect them was conducted. The results suggestedthe existence of PPR repeats of various formats, as well as smaller,PPR-unrelated repeats. Besides their length, these repeats differed in aminoacid arrangements and location of key amino acids. These findings provide abroader and unified perspective of the pentatricopeptide family while raisingprovocative questions about the assembly and evolution of these domains.