Co-Expression of a Precursor and the Mature Protein of Wheat Ribulose-1, 5-bisphosphate Carboxylase Small Subunit from a Single Gene in Escherichia coli

ABSTRACT The cDNA encoding a precursor of wheat ribulose-1,5-bisphosphate carboxylase/oxygenase was inserted in-phase with prokaryotic expression elements in four different vectors. Five expression vectors encoding the small subunit precursors were cloned in Escherichia coli. None of these constructs expressed detectable amounts of the precursor protein, but all directed synthesis of the mature small subunit. The expression of the small subunit was a consequence of an independent, intragenic Shine-Dalgarno sequence optimally located upstream from an ATG specifying the first codon of the mature small subunit portion in the precursor transcript. Similar internal translation signals have been identified in the nuclear-encoded cDNAs of the small-subunit precursors of numerous higher plant genes. The 5′ end of the wheat small-subunit precursor was linked with a consensus E. coli DNA sequence such that the modified gene encoded a partial hybrid precursor carrying four additional residues at its amino terminus. ...