Abstract
ABSTRACT Translation factor a/eIF5A is highly conserved in Eukarya and Archaea. The eukaryal eIF5A protein is required for transit of ribosomes across consecutive proline codons, whereas the function of the archaeal orthologue remains unknown. Here, we provide a first hint for an involvement of Sulfolobus solfataricus (Sso) aIF5A in translation. CRISPR-mediated knock down of the aif5A gene resulted in strong growth retardation, underlining a pivotal function. Moreover, in vitro studies revealed that Sso aIF5A is endowed with endoribonucleolytic activity. Thus, aIF5A appears to be a moonlighting protein that might be involved in protein synthesis as well as in RNA metabolism.
Highlights
The eukaryotic eIF5A and the bacterial orthologue EF-P were first identified as translation initiation factors [1]
We show that the protein associates with ribosomal subunits in a Sulfolobus solfataricus (Sso) cell lysate programmed for protein synthesis, providing a first indication that aIF5A might participate in translation
A cell lysate of Sso P2 was treated with formaldehyde and separated by 10–30% sucrose gradient centrifugation, and the individual fractions were probed for aIF5A with anti-aIF5A antibodies as well as with antibodies against aIF6, which served as a marker for 50S subunits [31]
Summary
The eukaryotic eIF5A and the bacterial orthologue EF-P were first identified as translation initiation factors [1]. Subsequent studies revealed that they affect translational elongation by alleviating ribosome stalling at poly-proline stretches [2,3] as well as translational termination [3]. It was further shown that the archaeal protein is either hypusinated or deoxyhypusinated, and that some Archaea contain both versions of the protein [6,7]. The 3D structures of eIF5A and aIF5A are very similar, with a strong conservation of residues in the N-terminal moiety that contains the eIF5A hypusination site [8]
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