Viral mutagenesis as a means for generating novel proteins.

We demonstrate that a mutation-prone virus engineered to express a foreign gene is an expedient means for generating novel mutant nonviral proteins in mammalian cells. Using vesicular stomatitis virus to express a gene coding for a fluorescent DsRed protein, a number of green mutant variants including a new variant not previously described were rapidly isolated from infected cells, sequenced, and cloned. Similar methods may be useful in the development of physiologically sensitive fluorescent reporter proteins and directed evolution or mutagenesis of proteins in general.