Leu3

Leu3 is a transcriptional regulator of leucine metabolism that belongs to the zinc cluster family. Leu3 binds to the DNA sequence CCGGNNCCGG in a manner that is independent of environmental conditions (Brisco and Kohlhaw, 1990; Friden et al., 1989; Kirkpatrick and Schimmel, 1995).

The transcriptional regulatory activity of Leu3 is mediated through its interaction with the small molecule 2-isopropylmalate, a biosynthetic precursor of leucine. Low concentrations of this compound result in transcriptional repression by Leu3, whereas higher concentrations lead to transcriptional activation (Sze et al., 1993; Sze et al., 1992). Association with 2-isopropylmalate is thought to result in changes in the structural conformation of Leu3 that lead to the changes in its regulatory activity (Sze and Kohlhaw, 1993; Wang et al., 1997).

Leu3 itself is likely transcriptionally regulated by Gcn4, the regulator of amino acid biosynthesis (Zhou et al., 1987).