CONSTRUCTION AND EXPRESSION OF A SYNTHETIC STREPTAVIDIN-ENCODING GENEIN ESCHERICHIA-COLI

A synthetic gene encoding 'core' streptavidin (SAV) [amino acid (aa) r esidues 13-140 of Streptomyces avidinii SAV] has been efficiently expr essed in Escherichia coli from the IPTG-inducible lac promoter of plas mid pET3a. In this system, expression levels are nearly tenfold greate r for the synthetic gene than for the corresponding native gene. The s ynthetic gene was constructed from overlapping oligodeoxyribonucleotid es whose sequences were optimized to incorporate codons preferred by h ighly expressed E. coli genes. Biochemical characterizations by gel me thods, aa analysis, N-terminal sequencing, and size exclusion chromato graphy show that the synthetic gene product purified by affinity chrom atography possesses the properties expected for core SAV.