ABSTRACT
The ultimate purpose of protein engineering is to produce proteins having desired functions. Traditional methods of protein engineering have involved random mutagenesis by using chemicals or radiation. These methods were used by molecular biologists in demonstrating how enzymes can be tailored for applications. However, in classical mutagenesis, most mutations are harmful or neutral, and for successful mutagenesis, it is important to avoid introducing many mutations in target genes. Therefore optimum tuning of the mutation rate is required in addition to screening large numbers of mutants (1). Another drawback of traditional mutagenesis methods is that point mutations can only introduce a limited range of amino-acid substitutions because of the nature of the codon table, and the expected frequency of a change from one amino acid to another is quite different for different types of amino acid substitutions. This limitation narrows the sequence space of mutant proteins that traditional mutagenesis methods can create.
