title: Identification of LACTB2, a metallo-β-lactamase protein, as a human mitochondrial endoribonuclease.
abstract: Post-transcriptional control of mitochondrial gene expression, including the processing and generation of mature transcripts as well as their degradation, is a key regulatory step in gene expression in human mitochondria. Consequently, identification of the proteins responsible for RNA processing and degradation in this organelle is of great importance. The metallo-β-lactamase (MBL) is a candidate protein family that includes ribo- and deoxyribonucleases. In this study, we discovered a function for LACTB2, an orphan MBL protein found in mammalian mitochondria. Solving its crystal structure revealed almost perfect alignment of the MBL domain with CPSF73, as well as to other ribonucleases of the MBL superfamily. Recombinant human LACTB2 displayed robust endoribonuclease activity on ssRNA with a preference for cleavage after purine-pyrimidine sequences. Mutational analysis identified an extended RNA-binding site. Knockdown of LACTB2 in cultured cells caused a moderate but significant accumulation of many mitochondrial transcripts, and its overexpression led to the opposite effect. Furthermore, manipulation of LACTB2 expression resulted in cellular morphological deformation and cell death. Together, this study discovered that LACTB2 is an endoribonuclease that is involved in the turnover of mitochondrial RNA, and is essential for mitochondrial function in human cells.
authors.affiliation: Faculty of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Shiri
authors.initials: S
authors.lastname: Levy
authors.affiliation: Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7DQ, UK.
authors.forename: Charles K
authors.initials: CK
authors.lastname: Allerston
authors.affiliation: Faculty of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Varda
authors.initials: V
authors.lastname: Liveanu
authors.affiliation: Faculty of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Mouna R
authors.initials: MR
authors.lastname: Habib
authors.affiliation: Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7DQ, UK opher.gileadi@sgc.ox.ac.uk.
authors.forename: Opher
authors.initials: O
authors.lastname: Gileadi
authors.affiliation: Faculty of Biology, Technion- Israel Institute of Technology, Haifa 32000, Israel gadis@tx.technion.ac.il.
authors.forename: Gadi
authors.initials: G
authors.lastname: Schuster
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics; D008928:Mitochondria / Q000201:enzymology*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000235:genetics; D000077278:RNA, Mitochondrial; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D001618:beta-Lactamases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D008667:Metalloproteins; D000077278:RNA, Mitochondrial; D016601:RNA-Binding Proteins; D012313:RNA; D004722:Endoribonucleases; C000607856:LACTB2 protein, human; D001618:beta-Lactamases
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