INVOLVEMENT OF A 50-KDA MRNP PROTEIN FROM SACCHAROMYCES-CEREVISIAE INMESSENGER-RNA BINDING TO RIBOSOMES

A yeast 50-kDa mRNA-binding protein (50mRNP) is found selectively asso ciated with the 48S and 80S initiation complexes. This protein is stru cturally related to the translational elongation factor EF-1 alpha. Th e protein reacts with antibodies directed against EF-1 alpha and, simi larly, EF-1 alpha recognizes antibodies against the 50mRNP protein. Th is is evidence that they share at least one epitope which allows a sim ilar antigenic behavior, In addition, both proteins show similar cleav age patterns upon treatment with the endoproteinase Lys-C. A murine an tibody raised against 50mRNP inhibits both 48S and 80S initiation comp lex formation. The inhibitory effect is relieved by preincubating anti -50mRNP with EF-1 alpha. Antibody to EF-1 alpha manifests a similar in hibitory pattern for the formation of 48S and 80S complexes. These dat a strongly suggest that 50mRNP is an EF-1 alpha-like polypeptide essen tial for the formation of the above complexes. (C) 1997 Academic Press .