Relationships between the major kinetoplastid paraflagellar rod proteins: a consolidating nomenclature!

The Kinetoplastida comprise a family of flagellated mi-crobes that are defined by the presence of a network of con-catenated mitochondrial DNA called the kinetoplast and a range of other unique features. One such is the paraflagel-lar rod (PFR), which has an essential role in cell motility [1–3], an intricate sub-structural arrangement [4,5] and an interesting phylogenetic distribution [6,7]. Although the complete composition of the PFR is still unknown, the major structural components have been de-scribed in several species of Kinetoplastida. The first bio-chemical description in kinetoplastids identified the two major PFR proteins, PFR1 and PFR2, in Crithidia fascic-ulata [8]. In that paper, PFR1 was defined as the protein with the slower migration in SDS–PAGE gels while the faster migrating band was called PFR2. Since then, other descriptions of major PFR proteins in trypanosomatids have been made, including those of Herpetomonas megaseliae [9], Trypanosoma species [10,11] and Leishmania species [12,13]. At the time of many of these publications the corre-lation between major PFR proteins of different species was unclear and nomenclatures developed that were peculiar to each species and did not reflect the homologies amongst the proteins (see Table 1). However, with the increasing avail-ability of DNA and protein sequences, we have now been able to define the levels of homology between PFR proteins (Fig. 1) and this reveals that the disconnected nomenclature!Note: Crithidia fasciculata sequence data reported in this paper are available in the GenBank under the accession numbers AY568293 (PFR2