Patent ID: 7390645

Claim:
An altered lac repressor protein, that: a) has an enhanced inducer responsivity relative to a wild-type lac repressor protein, wherein the altered lac repressor protein comprises the following amino acid changes relative to the wild-type lac repressor protein: Leu148Phe in combination with Asp274Asn; or b) has both an increased binding affinity for LacO DNA sequence and an enhanced inducer responsivity relative to a wild-type lac repressor protein, wherein the altered lac repressor protein comprises a combination of two or more amino acid changes, relative to the wild-type lac repressor protein, wherein the amino acid changes are selected from the group consisting of: Gln60Gly in combination with Leu148Phe, Gln60Gly in combination with Leu148Tyr, Gln60Gly in combination with Pro188Ser, Gln60Gly in combination with Leu296Met, Gln60Gly in combination with Leu296Ile, Gln60Gly in combination with Pro320Ala, Gln60Gly in combination with Pro320Gly, Gln60Gly in combination with Val321Ile, Gln60Gly in combination with Val321Leu, Gln60Gly in combination with Val321Met, and Gln60Gly in combination with Leu148Phe and Asp274Asn.