Antagonistic effects Na+ and Mg2+ on the structure, function, and stability of mycobacteriophage L1 repressor.
Temperate mycobacteriophage L1 encodes an unusual repressor (CI) for regulating its lytic-lysogenic switching and, in contrast to the repressors of most temperate phages, it binds to multiple asymmetric operator DNAs. Here, ions like Na(+), Cl(-), and acetate(-) ions were demonstrated to facilitate the optimal binding of CI to cognate operator DNA, whereas K(+), Li(+), NH4(+), Mg(2+), carbonate(2-), and citrate(3-) ions significantly affected its operator binding activity. Of these ions, Mg(2+) unfolded CI most severely at room temperature and, compared to Mg(2+), Na(+) provided improved thermal stability to CI. Furthermore, the intrinsic tryptophan fluorescence of CI was changed notably upon replacing Na(+) with Mg(2+) and these opposing effects of Mg(2+) and Na(+) were also noticed in their actions on the C-terminal fragment (CTD) of CI. Taken together, Na(+) appeared to be more appropriate than Mg(2+) for maintaining the biologically active conformation of CI needed for its optimal binding to operator DNA.
Bandhu
Amitava
A
Department of Biochemistry, Bose Institute, P1/12-CIT Scheme VII M, Kolkata 700 054, India.
Ganguly
Tridib
T
Chanda
Palas K
PK
Das
Malabika
M
Jana
Biswanath
B
Chakrabarti
Gopal
G
Sau
Subrata
S
D000085:Acetates / Q000378:metabolism; D002254:Carbonates / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism*; D009160:Mycobacteriophages / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D000085:Acetates; D002254:Carbonates; D002951:Citrates; D012097:Repressor Proteins; D014764:Viral Proteins; D012964:Sodium; D008274:Magnesium