Design of thermolabile bacteriophage repressor mutants by comparative molecular modeling.

Comparative molecular modeling was performed with repressor protein Rro of the temperate Lactococcus lactis bacteriophage r1t using the known 3D-structures of related repressors in order to obtain thermolabile derivatives of Rro. Rro residues presumed to stabilize a nonhomologous but structurally conserved hydrophobic pocket, which was shown to be important for thermostability of the Escherichia coli bacteriophage lambda repressor CI, were randomized. Of the derivatives that exhibited various temperature-sensitive phenotypes, one was shown to hold promise for both fundamental and industrial applications that require the controlled production of (heterologous) proteins in L. lactis.