Open AccessComplexes of Messenger RNA and 40‐S Subunit in Rabbit Reticulocytes
Author(s) -
ZehaviWillner Tova,
Da David
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb02678.x
Subject(s) - protein subunit , rna , messenger rna , transfer rna , density gradient , polysome , microbiology and biotechnology , nucleoprotein , chemistry , phosphate , biochemistry , ribosome , biology , gene , physics , quantum mechanics
Native 40‐S subunits isolated from reticulocytes of anemic rabbits exposed for 2 h to [ 32 P]‐phosphate are labelled to a much higher extent than are 60‐S subunits, monosomes and polysomes. Sucrose gradient analysis of the RNA content of these 40‐S subunits shows that most of the radioactivity appears in the 9‐S RNA peak. Analysis of native 40‐S subunits 40 h after [ 32 P]‐phosphate‐administration indicates, that in addition to 18‐S RNA as a major component, they also contain mRNA and tRNA. EDTA treatment releases from the native 40‐S subunits 9‐S RNA in the form of a 15‐S mRNA ṁ protein particle. CsCl gradient profiles of the subunits followed by base analysis of the fractions obtained on the gradient, revealed the presence of two forms of 40‐S subunits with buoyant densities of 1.436 (major peak) and 1.512 g/cm 3 (minor peak), respectively. It is proposed that the subunit particle with density of 1.436 g/cm 3 is a 40‐S mRNA ṁ protein ṁ tRNA initiation complex, in view of its buoyant density characteristics, the absence of nucleoprotein particles other than the forms of 40‐S subunits and the molar ratio of the three components in the complex.