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Maturase K (matK) is a plant plastidial gene. The protein it encodes is an organelle intron maturase, a protein that splicesGroup II introns. It is essential for in vivo splicing of Group II introns. Amongst other maturases, this protein retains only a well conserved domain X and remnants of a reverse transcriptase domain.
LtrA, an open reading frame found in the Lactococcus lactis group II introns LtrB. It is an intron-encoded protein, with three subdomains, one of which is a reverse-transcriptase/maturase.