A cDNA for nuclear-encoded chloroplast translational initiation factor 2 from a higher plant is able to complement an infB Escherichia coli null mutant.
Formation of the initiation translation complex containing the three initiation factors, IF1, IF2, and IF3, tRNA(fMet), and GTP constitutes the earliest event in the protein synthesis. IF2, a GTP-binding protein, is the principal factor involved in selecting and binding fMet-tRNA(fMet) to the 30 S ribosomal subunit. Although some chloroplast initiation translational factors have been identified and purified from algae, none of these factors have been characterized from plants. In this work, we report the molecular characterization of a nuclear-encoded chloroplastic IF2 gene from common bean (PvIF2cp). We show that the PvIF2cp gene encodes a protein containing a chloroplast translocation signal peptide, able to target a green fluorescent protein fusion protein to chloroplasts. A high accumulation of PvIF2cp transcript was found in photosynthetic tissues, whereas low mRNA levels were detected in etiolated plants and in nonphotosynthetic organs. Additional data indicate that the PvIF2cp transcript accumulation is modulated by light. The PvIF2cp gene encodes a functional factor, since the PvIF2cp conserved region, containing the G-domain and the C-terminal end, complements an Escherichia coli infB null mutation. Phylogenetic analysis using the PvIF2cp conserved region suggests that the PvIF2cp gene originated via endosymbiotic gene transfer to the nucleus and that it may be a useful marker for phylogeny reconstruction.
Campos
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Departamento de Biologia Molecular de Plantas del Instituto de Biotecnologia, Universidad Nacional Autónoma de México, A. P. 510-3, Cuernavaca, Morelos 62250, México.
García-Gómez
B I
BI
Solórzano
R M
RM
Salazar
E
E
Estevez
J
J
León
P
P
Alvarez-Buylla
E R
ER
Covarrubias
A A
AA
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D001692:Biological Transport; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D015723:Gene Library; D017343:Genes, Plant; D005816:Genetic Complementation Test; D005819:Genetic Markers; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010448:Peptide Initiation Factors / Q000737:chemistry* / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics; D010802:Phylogeny; D010947:Plants, Toxic; D039881:Prokaryotic Initiation Factor-2; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014018:Tissue Distribution; D014026:Nicotiana / Q000235:genetics
D018076:DNA, Complementary; D005819:Genetic Markers; D008164:Luminescent Proteins; D010448:Peptide Initiation Factors; D039881:Prokaryotic Initiation Factor-2; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins