Ny. Sidorova et Dc. Rau, DIFFERENCES IN WATER RELEASE FOR THE BINDING OF ECORI TO SPECIFIC ANDNONSPECIFIC DNA-SEQUENCES, Proceedings of the National Academy of Sciences of the United Statesof America, 93(22), 1996, pp. 12272-12277
The free energy difference between complexes of the restriction nuclea
se EcoRI with nonspecific DNA and with the enzyme's recognition sequen
ce is linearly dependent on the water chemical potential of the soluti
on, set using several very different solutes, ranging from glycine and
glycerol to triethylene glycol and sucrose. This osmotic dependence i
ndicates that the nonspecific complex sequesters some 110 eaters more
than the specific complex with the recognition sequence. The insensiti
vity of the difference in number of waters released to the solute iden
tity further indicates that this water is sequestered in a space that
is sterically inaccessible to solutes, most likely at the protein-DNA
interface of the nonspecific complex. Calculations based on the struct
ure of the specific complex suggest that the apposing DNA and protein
surfaces in the nonspecific complex retain approximately a full hydrat
ion layer of water.