Transfer of Valine into Rabbit Haemoglobin from Various Isoaccepting Species of Valyl-tRNA Differing in Codon Recognition.

The transfer of valine into haemoglobin from various isoaccepting species of Val-tRNA obtained from Escherichia coli and yeast, which differ in the specificity for codon recognition has been investigated using a rabbit reticulocyte cell-free system. It was demonstrated that the Val-tRNA species which bind to ribosomes in response to the codon GUG preferentially transferred valine into both a and β-globin chains and that the other species of Val-tRNA which cannot repond to GUG were scarcely utilized in the haemoglobin synthesis. Several possibilities to explain this phenomenon were examined and consequently it has been strongly suggested that valine codons in mRNA for rabbit globin, at least for α-globin chain, are very rich in GUG and possibly GUA. [ABSTRACT FROM AUTHOR]