Section 71
Chapter 70,207

Purification and properties of a protein component of messenger ribonucleoprotein particles that shares a common epitope with eucaryotic elongation factor Tu

Slobin, L.I.; Greenberg, J.R.

FEBS Journal 173(2): 305-310


ISSN/ISBN: 1742-464X
DOI: 10.1111/j.1432-1033.1988.tb13999.x
Accession: 070206998

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A 62-kDa polypeptide, which reacts with antibodies directed against a peptide corresponding to a portion of the amino-terminal structure of eucaryotic elongation factor Tu (eEF-Tu), was purified from the 0.5 M NaCl wash of rabbit reticulocyte polysomes. Previous work has shown that this polypeptide is a constituent of messenger ribonucleoprotein particles (mRNPs) from a variety of mammalian cell types [Greenberg, J.R. and Carroll, E. C. (1985) Mol. Cell Biol. 5, 342-351]. The purified polypeptide bound mRNA as well as rRNA using a nitrocellulose-filter assay. The same nitrocellulose-filter assay failed to detect binding to GTP. Using a competition-binding assay, it was established that the purified polypeptide interacts with poly(U) and poly(G) but not with poly(A). This preference for synthetic polynucleotides was the same as found for eEF-Tu [Slobin, L.I. (1983) J. Biol. Chem. 258, 4895-4900]. Furthermore, treatment of the purified RNA-binding protein with trypsin resulted in a rapid cleavage of two peptide bonds resulting in fragments of 60 kDa and 53 kDa. Trypsin also cleaves eEF-Tu rapidly at two bonds resulting in two large polypeptide fragments [Slobin, L.I., Clark, R.V. & Olson, M.O.J. (1981) Biochemistry 20, 5761-5767]. The amino acid sequence of the first 39 residues of the purified RNA-binding protein was determined and found to possess no homology to eEF-Tu.

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