title: A mitochondrial-like targeting signal on the hydrogenosomal malic enzyme from the anaerobic fungus Neocallimastix frontalis: support for the hypothesis that hydrogenosomes are modified mitochondria.
abstract: The hydrogenosomal malic enzyme (ME) was purified from the anaerobic fungus Neocallimastix frontalis. Using reverse genetics, the corresponding cDNA was isolated and characterized. The deduced amino acid sequence of the ME showed high similarity to ME from metazoa, plants and protists. Putative functional domains for malate and NAD+/NADP+ binding were identified. Phylogenetic analysis of the deduced amino acid sequence of the new ME suggests that it is homologous to reference bacterial and eukaryotic ME. Most interestingly, the cDNA codes for a protein which contains a 27-amino-acid N-terminus which is not present on the purified mature protein. This presequence shares features with known mitochondrial targeting signals, including an enrichment in Ala, Leu, Ser, and Arg, and the presence of an Arg at position-2 relative to amino acid 1 of the mature protein. This is the first report of a mitochondrial-like targeting signal on a hydrogenosomal enzyme from an anaerobic fungus and provides support for the hypothesis that hydrogenosomes in Neocallimastix frontalis might be modified mitochondria.
authors.affiliation: University of Groningen, Department of Microbiology, Haren, The Netherlands. m.van.der.giezen@biol.rug.nl
authors.forename: M
authors.initials: M
authors.lastname: van der Giezen
authors.forename: K B
authors.initials: KB
authors.lastname: Rechinger
authors.forename: I
authors.initials: I
authors.lastname: Svendsen
authors.forename: R
authors.initials: R
authors.lastname: Durand
authors.forename: R P
authors.initials: RP
authors.lastname: Hirt
authors.forename: M
authors.initials: M
authors.lastname: Fèvre
authors.forename: T M
authors.initials: TM
authors.lastname: Embley
authors.forename: R A
authors.initials: RA
authors.lastname: Prins
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D004271:DNA, Fungal; D005658:Fungi / Q000201:enzymology* / Q000235:genetics; D015723:Gene Library; D006801:Humans; D008291:Malate Dehydrogenase / Q000145:classification / Q000235:genetics*; D008928:Mitochondria; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D018076:DNA, Complementary; D004271:DNA, Fungal; D008291:Malate Dehydrogenase; C046446:malate dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); C030574:malate dehydrogenase (decarboxylating); C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)