Ty1 and IN structure. The structure of the Ty1 retrotransposon is diagrammed. Black triangles indicate the long-terminal-repeat regions. The GAG and POL ORFs and the element-encoded proteins derived from POL are indicated. The complete sequence of Ty1 IN is shown. Restriction site abbreviations: S, SalI; B, BglII; C, ClaI; E, EcoRI; K, KpnI; P, PvuII. The amino acid number is indicated beneath each restriction site. Key restriction sites are indicated above the corresponding amino acid sequence. IN NLS mutations, B1 and B2, made in the GAL-Ty1 plasmid are in boldface type. The numbers to the right of the sequence represent the last amino acid residue on that line of sequence.