Variants within the yeast Ty sequence family encode a class of structurally conserved proteins

The Ty transposable elements of Saccharomyces cerevisiae form a heterogeneous family within which two broad structural classes (I and II) exist. The two classes differ by two large substitutions and many restriction sites. We show that, like class I elements a class II element, Tyl-17, also appears to contain at least two major protein coding regions, designated TYA and TYB, and the organisational relationship of these regions has been conserved. The TYA genes of both classes encode proteins, designated p1 proteins, with an approximate molecular weight of 50 Kd and, despite considerable variation between the TYA regions at the DNA level, the structures of these proteins are remarkably similar. These observations strongly suggest that the p1 proteins of Ty elements are functionally significant and that they have been subject to selection.