An archaeal protein with homology to the eukaryotic translation initiation factor 5A shows ribonucleolytic activity.
To identify proteins that are involved in RNA degradation and processing in Halobacterium sp. NRC-1, we purified proteins with RNA-degrading activity by classical biochemical techniques. One of these proteins showed strong homology to the eukaryotic initiation factor 5A (eIF-5A) and was accordingly named archaeal initiation factor 5A (aIF-5A). Eukaryotic IF-5A is known to be involved in mRNA turnover and to bind RNA. Hypusination of eIF-5A is required for sequence-specific binding of RNA. This unique post-translational modification is restricted to Eukarya and Archaea. The exact function of eIF-5A in RNA turnover remained obscure. Here we show for the first time that aIF-5A from Halobacterium sp. NRC-1 exhibits RNA cleavage activity, preferentially cleaving adjacent to A nucleotides. Detectable RNA binding could be shown for aIF-5A purified from Halobacterium sp. NRC-1 but not from Escherichia coli, while both proteins possess RNA cleavage activity, indicating that hypusination of aIF-5A is required for RNA binding but not for its RNA cleavage activity. Furthermore, we show that the hypusinated form of eIF-5A also shows RNase activity while the unmodified protein does not. Charged amino acids in the N-terminal domain of aIF-5A as well as in the C-terminal domain, which is highly similar to the cold shock protein A (CspA), an RNA chaperone of E. coli, are important for RNA cleavage activity. Moreover our results reveal that activity of aIF-5A depends on its oligomeric state.
Wagner
Steffen
S
Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Klug
Gabriele
G
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002478:Cells, Cultured; D005057:Eukaryotic Cells; D005822:Genetic Vectors; D006217:Halobacterium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008024:Ligands; D008239:Lysine / Q000031:analogs & derivatives / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D019642:RNA, Archaeal / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012260:Ribonucleases / Q000235:genetics / Q000378:metabolism*; D012689:Sequence Homology, Nucleic Acid; D000097574:Eukaryotic Translation Initiation Factor 5A
D019843:Archaeal Proteins; D008024:Ligands; D008239:Lysine; D010448:Peptide Initiation Factors; D019642:RNA, Archaeal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012260:Ribonucleases; D000097574:Eukaryotic Translation Initiation Factor 5A; C100028:hypusine