Easy two-step method for randomizing and cloning gene fragments.

Random mutagenesis is widely used in protein engineering to improve or alter protein function. Creating random mutant libraries typically requires cloning of randomly mutagenized fragments into an expression vector, which is laborious and often hampered by lack of unique and convenient restriction sites. Here, we report an easy two-step method that produces a more balanced mutational spectrum and simplifies the cloning of randomly mutagenized genes or gene fragments for constructing high titer random mutant libraries.