An operator-induced conformational change in the C-terminal domain of the lambda repressor.
4,4'-bis(1-anilino-8-naphthalenesulfonic acid (Bis-ANS), an environment-sensitive fluorescent probe for hydrophobic region of proteins, binds specifically to the C-terminal domain of lambda repressor. The binding is characterized by positive cooperativity, the magnitude of which is dependent on protein concentration in the concentration range where dimeric repressor aggregates to a tetramer. In this range, positive cooperativity becomes more pronounced at higher protein concentrations. This suggests a preferential binding of Bis-ANS to the dimeric form of the repressor. Binding of single operator OR1 to the N-terminal domain of the repressor causes enhancement of fluorescence of the C-terminal domain bound Bis-ANS. The binding of single operator OR1 also leads to quenching of fluorescence of tryptophan residues, all of which are located in the hinge or the C-terminal domain. Thus two different fluorescent probes indicate an operator-induced conformational change which affects the C-terminal domain. The significance of this conformational change with respect to the function of lambda repressor has been discussed.
Saha
R
R
Department of Biophysics, Bose Institute, Calcutta, India.
Banik
U
U
Bandopadhyay
S
S
Mandal
N C
NC
Bhattacharyya
B
B
Roy
S
S
D000817:Anilino Naphthalenesulfonates; D010582:Bacteriophage lambda / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D007700:Kinetics; D008433:Mathematics; D009876:Operon; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry*; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry; D014357:Trypsin; D014508:Urea; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
D000817:Anilino Naphthalenesulfonates; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; C035763:5,5'-bis(8-(phenylamino)-1-naphthalenesulfonate); D014508:Urea; D014357:Trypsin