The Thermococcus litoralis 4-alpha-glucanotransferase (GTase) gene has a high content of AGA and AGG codons for arginine, which are extremely rare in Escherichia coli, Expression of the GTase gene in E, coli resulted in low protein production and the accumulation of inclusion bodies. However, simultaneous expression of GTase with tRNA(AGA), tRNA(AGG) and GroELS affected both the production and solubility of GTase, and production of soluble GTase increasing about 5-fold. This nem E, coli expression system should be applicable to the expression of not only archaeal but also eukaryotic genes, which usually contain a large number of AGA and AGG codons. (C) 1999 Federation of European Biochemical Societies.