Fig 1. The SpTrf proteins are highly variable.

Examples of different SpTrf protein isoforms are shown as a cartoon alignment. All proteins include a hydrophobic leader and the mature protein, which is a mosaic of sequence blocks or elements (indicated as colored rectangles) that make up mosaics of element patterns. All possible elements are shown at the top, although the SpTrf proteins never include all possible elements. The patterns correlate with the sequence of element 10 that is highly diverse and is used to define the pattern type [36]. Mature SpTrf proteins consist of a glycine-rich region with a multimerization region, a histidine-rich region, and a C-terminal region. rSpTrf-E1 has an E1 element pattern, which has been rarely identified. Some proteins are truncated as an outcome of RNA editing that generates frameshifts and inserts stop codons [54], the most common of which is an edit that creates a stop codon in element 8 (indicated by the star) for the E2 pattern. This figure is modified from Buckley & Smith [48].