A correlation between efficacy of gene expression and nucleotide compositio
n of its protein-coding sequences was studied. It was found that measures b
ased exclusively on codon frequencies are analogous to codon adaptation ind
ex [1] and do not adequately reveal this correlation. A more general measur
e is suggested, i.e., elongation efficacy index, which takes into account b
oth the codon frequencies and the level of local mRNA complementarity. Util
ization of this measure facilitated adequate recognition of highly expresse
d genes in 18 unicellular organisms, i.e., 14 eubacteria, three archaebacte
ria, and yeast.