Cloning and characterization of the gene encoding beta subunit of mitochondrial processing peptidase from the basidiomycete Lentinula edodes

We have isolated the gene encoding the beta subunit of mitochondrial processing peptidase (β-MPP) from the shiitake mushroom Lentinula edodes. It is a nuclear gene with two small introns. Comparison with known β-MPP genes revealed that the L. edodes gene is most closely related with that from Neurospora crassa, with 60.8% identities and 87% similarity in the amino-acid sequences. The deduced L. edodes β-MPP peptide sequence contains the inverse zinc-binding motif (H–X–E–H) that has been found in a large family of zinc-binding metalloproteinases including bacterial proteinases, insulin degrading enzymes and β-MPPs. The two histidines are thought to contribute two of the three residues for zinc binding. The expression of L. edodes β-MPP is higher during the development of the fruiting bodies, suggesting that higher mitochondrial activities may be required to meet the energy demand in the rapid growth of the fruiting bodies.