Association of ribosomal subunits
Open Access
- 1 September 1991
- journal article
- Published by Wiley in European Journal of Biochemistry
- Vol. 200 (2) , 321-327
- https://doi.org/10.1111/j.1432-1033.1991.tb16188.x
Abstract
A yeast ribosomal subunit association factor (AF) has been purified from a high-salt ribosomal wash. The purified enzyme is a thermostable protein that associates ribosomal subunits at low Mg2+ concentration without requiring energy. It appears to be an aggregate of trimers or dimers (molecular mass 125 or 79 kDa) which on sodium dodecyl sulfate gels shows the presence of a major protein band whose estimated molecular mass is 43 kDa. Evidence also indicates the existence of a 50-kDa polypeptide which seems to be unstable since with freezing and thawing it gives rise to the 43-kDa polypeptide. It was shown that the labelled factor interacts with 80S ribosomes and with 40S ribosomal subunits. The purified polypeptide reacts with antibodies directed against EF-1 alpha, this last protein recognizing the antibodies raised against AF. Likewise, both EF-1 alpha and AF associate ribosomal subunits in the same way. When EF-1 is heated, it not only maintains its association activity, but also behaves like a 43-kDa polypeptide in an SDS electrophoresis run. These observations strongly suggest that AF originates from EF-1 alpha, which implies that the well-known elongation factor may also play a role in the initiation step of protein synthesis.Keywords
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