These proteins have, like many other proteins, modular structures. Thus, their DNA binding domains are well separated from their aggregation domains.
Dimers react with DNA targets of dyadic symmetry, tetramers with two DNA targets of dyadic symmetry.
It was our goal to understand as well as possible the functions and interactions of these six proteins with their modular partners. The two X-ray structures which recently became available by Friedmann et al. So, I wrote a book on Lac R and its history. Furthermore we published four papers dealing with this protein. For the isolation of Lac R in 1996 I had selected a mutant which bound inducer IPTG about twofold better than the wild type Lac R in vivo and in vitro .