Ndt80 is a Saccharomyces cerevisiae meiosis-specific transcription factor responsible for promoting the stage-specific expression of a family of genes referred to as middle sporulation genes. Many members of this gene family are essential for the completion of meiotic chromosome segregation. Thus, Ndt80 is essential for the completion of meiosis. Ndt80 is highly regulated both transcriptionally and post-translationally. To facilitate biochemical analysis of Ndt8O, we have expressed the DNA binding domain in Escherichia coli and purified the recombinant protein with an affinity chromatography procedure. In addition we have dissected the amino-terminus of Ndt8O to delimit the functional DNA binding domain. This analysis shows that the amino-terminal 40 amino-acids of Ndt8O, although not essential for its DNA binding activity, do have an effect on its ability to bind specifically to its target DNA sequence. In addition, we show that the Ndt80 DNA binding domain can be phosphorylated by the meiosis-specific protein kinase Ime2 in vitro, but contrary to our initial hypothesis this phosphorylation does not significantly affect the affinity of Ndt8O for its target DNA sequence. (C) 2003 Elsevier Inc. All rights reserved.