NMR STRUCTURE OF A SPECIFIC DNA COMPLEX OF ZN-CONTAINING DNA-BINDING DOMAIN OF GATA-1

The three-dimensional solution structure of a complex between the DNA binding domain of the chicken erythroid transcription factor GATA-1 an d its cognate DNA site has been determined with multidimensional heter onuclear magnetic resonance spectroscopy. The DNA binding domain consi sts of a core which contains a zinc coordinated by four cysteines and alpha carboxyl-terminal tail. The core is composed of two irregular an tiparallel beta sheets and an ot helix, followed by a long loop that l eads into the carboxyl-terminal tail. The amino-terminal part of the c ore, including the helix, is similar in structure, although not in seq uence, to the amino-terminal zinc module of the glucocorticoid recepto r DNA binding domain. In the other regions, the structures of these tw o DNA binding domains are entirely different. The DNA target site in c ontact with the protein spans eight base pairs. The helix and the loop connecting the two antiparallel beta sheets interact with the major g roove of the DNA. The carboxyl-terminal tail, which is an essential de terminant of specific binding, wraps around into the minor groove. The complex resembles a hand holding a rope with the palm and fingers rep resenting the protein core and the thumb, the carboxyl-terminal tail. The specific interactions between GATA-1 and DNA in the major groove a re mainly hydrophobic in nature, which accounts for the preponderance of thymines in the target site. A large number of interactions are obs erved with the phosphate backbone.