TnlOtetoperator mutations affecting Tetrepressor recognition

Theeffect ofsingle basepairalterations oftheTnlOencoded tetope- ratoronrecognition ofTetrepressor was studied invivousinga repres- sortitration systemandinvitrobydissociation ratedeterminations of therespective complexes. Bothmethods reveal thatthetwooperators, 0 and02,whichareinatandem arrangement inthewildtype,arerecognized withatwo-fold different affinity whenseparated. Studies onsynthetic operator sequences indicate thattheTetrepressor bindswithhigher affi- nitytothenon-palindromic 02wildtype thantotherespective palindromic sequences. Theinvivorepressor titration systemlinkstheexpression of lacZtotheaffinity oftetoperator toTetrepressor. Itwasusedtoiso- latetetoperator mutations withreduced affinity totherepressor. Thein vivoa-nd invitroobtained results withthesemutants agreequantitativeTy andindicate, thattheGCbasepairsatpositions 2,6,and8 areinvolved ininteraction withtheTetrepressor. Theirimportance forrecognition decreases inthatorder.Transitions atposition 7 ofthetetoperator show smaller effects onrecognition thantransversions.