Association of ribosomal subunits. A new functional role for yeast EF-1 alpha in protein biosynthesis.
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.
Herrera
F
F
Centro de Investigaciones Biomédicas (BIOMED), Facultad de Ciencias de la Salud, Universidad de Carabobo, Venezuela.
Correia
H
H
Triana
L
L
Fraile
G
G
D015153:Blotting, Western; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000096:biosynthesis*; D008970:Molecular Weight; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000502:physiology*; D012261:Ribonucleoproteins / Q000502:physiology; D012270:Ribosomes / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000502:physiology*
D005656:Fungal Proteins; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D012261:Ribonucleoproteins