Molecular cloning and sequence determination of the tuf gene coding for the elongation factor Tu of Thermus thermophilus HB8

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Abstract
The tuf gene, which encodes the elongation factor Tu (EF‐Tu) of Thermus thermophilus HB8, and its flanking regions were cloned and sequenced. The gene encoding EF‐G was found upstream of the 5′ end of the tuf gene. The tuf gene of T. thermophilus HB8 had a very high G + C content and 84.5% of the third base in codon usage was either G or C. The deduced primary structure of the EF‐Tu was composed of 405 amino acid residues with a Mr= 44658. A comparison of the amino acid sequence of EF‐Tu from T. thermophilus HB8 with those of Escherichia coli and Saccharomyces cerevisiae mitochondria showed a very high sequence homology (65–70%). Two Cys residues out of the three found in E. coli EF‐Tu had been replaced with Val in T. thermophilus HB8 EF‐Tu. An extra amino acid sequence of ten residues, consisting predominantly of basic amino acids (Met‐182–Gly‐191), which does not occur in EF‐Tu of E. coli, was found in T. thermophilus HB8.