Open AccessProtein synthesis in yeast Saccharomyces cerevisiae
Author(s) -
NASRIN Nargis,
AHMAD Mir Firoz,
NAG Mihir K.,
TARBURTON Philip,
GUPTA Naba K.
Publication year - 1986
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1986.tb10116.x
Subject(s) - ribosome , messenger rna , chemistry , eukaryotic small ribosomal subunit , yeast , biochemistry , biology , rna , gene
Antibodies prepared against a homogeneous preparation of Co‐eIF‐2A 20 [Ahmad et al. (1985) J. Biol. Chem. 260 , 6955–6959] reacted with several polypeptides including an 80‐kDa polypeptide present in a crude yeast ribosomal salt wash. This 80‐kDa polypeptide, containing Co‐eIF‐2A (Co‐eIF‐2A 80 ) activity, has been extensively purified using a two‐step purification procedure involving an immunoaffinity column chromatograph prepared using antibodies against Co‐eIF‐2A 20 (fraction II) and hydroxyapatite chromatography (fraction III). The factors, eIF‐2 + homogeneous Co‐eIF‐2A 80 (fraction III) promoted Met‐tRNA f · 40S complex formation with an AUG codon but not with a physiological mRNA or a polyribonucleotide messenger poly(U,G) whereas eIF‐2 + a partially purified Co‐eIF‐2A 80 preparation (fraction II) promoted Met‐tRNA f · 40S complex formation with an AUG codon as well as with globin mRNA and poly(U,G) messenger. This factor‐promoted Met‐tRNA f binding to 40S ribosomes depends absolutely on the presence of a polyribonucleotide messenger containing an initiation codon (such as AUG or GUG). Other polyribonucleotide messengers tested, such as poly(U), poly(A) and poly(A,C), were completely ineffective in this binding reaction. This result indicates that the Met‐tRNA f · 40S · mRNA complex is formed by a direct interaction between Met‐tRNA f , 40S ribosomes and the initiation site in mRNA. A mechanism has been proposed for Met‐tRNA f · 40S · mRNA complex formation in yeast.