Molecular modelling of protein-nucleic acid interactions.

Computer modeling techniques to study the interaction of proteins with nucleic acids are presented. The methods utilize information from genetic and chemical modification experiments and macromolecular structural constraints. These techniques, in addition to computer model building procedures and theoretical energy calculations, are illustrated for the study of the lac and cro repressor-operator systems. Our predicted interactions between lac and its operator agree with those recently reported for lac based upon sequence alignment with the cro repressor. Several molecular models of the putative helical segment of cro interacting with its OR3 operator are presented. These models are reflective of intermediate conformations experienced by the repressor in recognition of the operator sequence. The results of our studies are further discussed in terms of the design of short peptides interacting with nucleic acid sequences and the evolutionary requirements in establishing these repressor interactions.