title: A single mutation in the IF3 N-terminal domain perturbs the fidelity of translation initiation at three levels.
abstract: Bacterial translation initiation factor 3 (IF3) is involved in the fidelity of translation initiation at several levels, including start-codon discrimination, mRNA translation, and initiator-tRNA selection. The IF3 C-terminal domain (CTD) is required for binding to the 30S ribosomal subunit. N-terminal domain (NTD) function is less certain, but likely contributes to initiation fidelity. Point mutations in either domain can decrease initiation fidelity, but C-terminal domain mutations may be indirect. Here, the Y75N substitution mutation in the NTD is examined in vitro and in vivo. IF3(Y75N) protein binds 30S subunits normally, but is defective in start-codon discrimination, inhibition of initiation on leaderless mRNA, and initiator-tRNA selection, thereby establishing a direct role for the IF3 NTD in these initiation processes. A model illustrating how IF3 modulates an inherent function of the 30S subunit is discussed.
authors.affiliation: Department of Microbiology, Immunology, and Molecular Genetics, University of California-Los Angeles, 1602 Molecular Science, Los Angeles, CA 90095, USA.
authors.forename: Dianna
authors.initials: D
authors.lastname: Maar
authors.forename: Dionysios
authors.initials: D
authors.lastname: Liveris
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Sussman
authors.forename: Steven
authors.initials: S
authors.lastname: Ringquist
authors.forename: Isabella
authors.initials: I
authors.lastname: Moll
authors.forename: Nicholas
authors.initials: N
authors.lastname: Heredia
authors.forename: Angela
authors.initials: A
authors.lastname: Kil
authors.forename: Udo
authors.initials: U
authors.lastname: Bläsi
authors.forename: Ira
authors.initials: I
authors.lastname: Schwartz
authors.forename: Robert W
authors.initials: RW
authors.lastname: Simons
mesh_terms: D020121:5' Untranslated Regions / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000378:metabolism*; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D039665:Prokaryotic Initiation Factor-3 / Q000737:chemistry* / Q000235:genetics*; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012358:RNA, Transfer, Met / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D050505:Mutant Proteins; D039665:Prokaryotic Initiation Factor-3; D012358:RNA, Transfer, Met