Fig. 5

Eukaryotic inteins vary greatly in size. a Diversity of eukaryotic intein types. Inteins are classified into three types: HEN(−), HEN(+), or HEN(+)^extra. HEN(−) inteins contain the four conserved splicing blocks (A, B, F, and G) [50, 79]. Some have linker sequences between block B and F, such as the C. gattii Prp8 intein. HEN(+) inteins are full-length, and additionally encode blocks C, D, E, and H for the LAGLIDADG HEN domain. The HEN(+)^extra inteins are large, rarely described inteins that have stretches of linker domains or repeat sequences of unknown function. The only examples of HEN(+)^extra inteins in eukaryotes are in Prp8. b All eukaryal inteins in nDNA (red), cpDNA (green), or vDNA (blue) ordered by residue length (totaling 393 inteins). The nDNA inteins show the greatest size diversity, having HEN(−), HEN(+), and the only inteins in the HEN(+)^extra category. cpDNA inteins are overwhelmingly HEN(−). vDNA inteins fall between the sizes of nDNA and cpDNA inteins mainly in the range of HEN(+). c Inteins in specific exteins cluster by size. When inteins from specific exteins are plotted as a function of residue length, most cluster in the same HEN category, e.g. VMA1i are all HEN(+). Prp8i are the major exception, where inteins range across all three HEN types. Extein abbreviations are listed in Fig. 3 legend