| 摘要 |
<p>Certain aspects of the invention provide nucleic acid constructs that can be used to cause a cell to be dependent on a particular enzymatic activity or on the presence of a particular small molecule. Certain aspects of the invention also provide methods for cloning genes involved in the synthesis, modification or degradation of a given molecule and for the directed evolution of proteins that perform a specified enzymatic function. Certain methods of the invention can be used to isolate the genes responsible for directing the biosynthesis, modification or degradation of a particular target molecule and to isolate polypeptide variants having new or improved enzymatic activity.</p> |
