As part of the mitochondrial 3' processome (MPsome), involved in the maturation of guided RNA (gRNA) precursors. Component of the mitochondrial 3' processome (MPsome) complex composed at least of terminal uridylyltransferase KRET1/TUT1, 3'-5' exonuclease DSS1, MPSS1, MPSS2 and MPSS3 (PubMed:26833087). Within the complex, interacts with DSS1 (PubMed:26833087). Expressed at the procyclic stage (at protein level). RNAi-mediated knockdown at the procyclic stage causes moderate growth defect and reduces production of guided RNAs (gRNA) due to a block in the processing of gRNA precursors.