title: NAD-dependent methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase is targeted to the cytoplasm in insect cell lines.
abstract: Cytosolic NADP-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase synthetase and the mitochondrial NAD-dependent methylenetetrahydrofolate dehydrogenase-cyclohydrolase (NMDMC) are differentially expressed during insect development although both enzymes are detectable at all stages. In contrast, cell lines derived from a variety of insect species express high levels of NMDMC but undetectable levels of the NADP-dependent enzyme. Northern analysis indicates the NMDMC message is expressed at levels 50-100 times higher in a Drosophila cell line compared to adult flies. RNase protection showed the predominance of shortened transcripts that require initiation at a downstream AUG producing a truncated protein that lacks a mitochondrial targeting sequence. These changes in expression effectively exchange the cytosolic NADP-dependent dehydrogenase for one with NAD specificity.
authors.affiliation: Department of Biochemistry, McGill University, Montreal, QC, Canada.
authors.forename: G B
authors.initials: GB
authors.lastname: Tremblay
authors.forename: S S
authors.initials: SS
authors.lastname: Sohi
authors.forename: A
authors.initials: A
authors.lastname: Retnakaran
authors.forename: R E
authors.initials: RE
authors.lastname: MacKenzie
mesh_terms: D000595:Amino Acid Sequence; D000619:Aminohydrolases / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism*; D007313:Insecta / Q000201:enzymology*; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009838:Oligodeoxyribonucleotides; D017386:Sequence Homology, Amino Acid
chemical_list: D009097:Multienzyme Complexes; D009838:Oligodeoxyribonucleotides; C055342:methylene tetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase; D009243:NAD; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D000619:Aminohydrolases