High-level expression of a polypeptides encoded by a large segment of the envelope gene of HIV-1 in E-coli by directed evolution

A random mutagenesis library of gp120-801 (a large segment of the envelope protein gene of HIV-1) was constructed using error-prone PCR and DNA shuffl ing methods, and one mutant of gp120-801 was selected from this library usi ng a green fluorescent protein (GFP) fusion vector. After being cloned into pEX31b and expressed in E. coli, the expressed fusion protein reached to 1 5% of total bacterial proteins for the mutant but was just 1-2% for the wil d type.