title: A single mammalian mitochondrial translation initiation factor functionally replaces two bacterial factors.
abstract: The mechanism of translation in eubacteria and organelles is thought to be similar. In eubacteria, the three initiation factors IF1, IF2, and IF3 are vital. Although the homologs of IF2 and IF3 are found in mammalian mitochondria, an IF1 homolog has never been detected. Here, we show that bovine mitochondrial IF2 (IF2(mt)) complements E. coli containing a deletion of the IF2 gene (E. coli DeltainfB). We find that IF1 is no longer essential in an IF2(mt)-supported E. coli DeltainfB strain. Furthermore, biochemical and molecular modeling data show that a conserved insertion of 37 amino acids in the IF2(mt) substitutes for the function of IF1. Deletion of this insertion from IF2(mt) supports E. coli for the essential function of IF2. However, in this background, IF1 remains essential. These observations provide strong evidence that a single factor (IF2(mt)) in mammalian mitochondria performs the functions of two eubacterial factors, IF1 and IF2.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Gaur
authors.forename: Domenick
authors.initials: D
authors.lastname: Grasso
authors.forename: Partha P
authors.initials: PP
authors.lastname: Datta
authors.forename: P D V
authors.initials: PD
authors.lastname: Krishna
authors.forename: Gautam
authors.initials: G
authors.lastname: Das
authors.forename: Angela
authors.initials: A
authors.lastname: Spencer
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Agrawal
authors.forename: Linda
authors.initials: L
authors.lastname: Spremulli
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
mesh_terms: D000818:Animals; D002417:Cattle; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D039861:Prokaryotic Initiation Factor-1 / Q000235:genetics / Q000378:metabolism*; D039881:Prokaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D029968:Escherichia coli Proteins; D039642:Eukaryotic Initiation Factors; D024101:Mitochondrial Proteins; D039861:Prokaryotic Initiation Factor-1; D039881:Prokaryotic Initiation Factor-2