Non-catalytic subunit of the tRNA-splicing endonuclease complex, a complex responsible for identification and cleavage of the splice sites in pre-tRNA. It cleaves pre-tRNA at the 5' and 3' splice sites to release the intron. The products are an intron and two tRNA half-molecules bearing 2',3' cyclic phosphate and 5'-OH termini. There are no conserved sequences at the splice sites, but the intron is invariably located at the same site in the gene, placing the splice sites an invariant distance from the constant structural features of the tRNA body. May be required to embody the molecular ruler of the complex. tRNA splicing endonuclease is a heterotetramer composed of SEN2, SEN15, SEN34 and SEN54. Interacts directly with SEN2. The tRNA splicing endonuclease complex is predominantly associated with the outer membrane of mitochondria, suggesting that tRNA splicing mainly takes place on the mitochondrial surface. The tRNA splicing endonuclease complex is present with 100 molecules/cell. Present with 531 molecules/cell in log phase SD medium. Belongs to the SEN54 family.