Molecular Characterization of Mutants of the Acetate Regulatory GenefacBofAspergillus nidulans

Abstract

Todd, R. B., Kelly, J. M., Davis, M. A., and Hynes, M. J. 1997. Molecular characterization of mutants of the acetate regulatory genefacBofAspergillus nidulans.22,92–102. The facB gene ofAspergillus nidulansencodes a DNA binding transcriptional activator required for growth on acetate as a sole carbon source. FacB contains N-terminal GAL4-like Zn(II)2Cys6 (or C6 zinc) binuclear cluster DNA binding and leucine zipper-like heptad repeat motifs and central and C-terminal acidic α-helical regions.facBrecessive loss of function mutants are deficient in acetate induction of acetyl-CoA synthase, isocitrate lyase, malate synthase, acetamidase, and NADP-isocitrate dehydrogenase. Characterization of lesions infacBmutant alleles has localized important functional regions of the FacB protein. Two extreme mutants are shown to lack the C-terminal region of the protein. Two temperature sensitive mutants contain amino acid substitutions in the DNA binding domain and are shown to affect acetate induction ofamdS–lacZexpression and confer temperature sensitivein vitroDNA binding. Two temperature sensitivefacBmutations result in thermolability of acetyl-CoA synthase, isocitrate lyase, and malate synthase but not acetamidase or NADP-isocitrate dehydrogenase in crude extracts. This suggests that FacB may have a structural role in acetate metabolism in addition to its regulatory function.