Nucleic Acids Research, 1985, Vol. 13, No. 20 7483-7498
© 1985
Articles |
The catabolite activator protein stabilizes its binding site in the E. coli lactose promoter
Schools of Applied Biology and Physics, Georgia Institute of Technology Atlanta, GA 30332, USA
Received July 22, 1985. Accepted September 30, 1985.
The effect of catabolite activator protein, CAP, on the thermal stability of DNA was examined. Site specific binding was studied with a 62 bp DNA restriction fragment containing the primary CAP site of the E. coli lactose (1ac) promoter. A 144 bp DNA containing the 1ac promoter region and a 234 bp DNA from the pBR322 plasmid provided other DNA sites. Thermal denaturation of protein-DNA complexes was carried out in a low ionic strength solvent with 40% dimethyl aulfoxide, DMSO. In this solvent free DNA denatured below the denaturation temperature of CAP. The temperature stability of CAP for site specific binding was monitored using an acrylamide gel electrophoresis assay. Results show that both specific and non-specific CAP binding stabilize duplex DNA. Site specific binding to the 62 bp DNA produced a 13.3°C increase in the transition under conditions where non-specific binding stabilized this DNA by 2-3°C.