Molecular characterization of mutants of the acetate regulatory gene facB of Aspergillus nidulans.
The facB gene of Aspergillus nidulans encodes 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 alpha-helical regions. facB recessive 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 in facB mutant 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 of amdS-lacZ expression and confer temperature sensitive in vitro DNA binding. Two temperature sensitive facB mutations 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.
Todd
R B
RB
Department of Genetics, The University of Melbourne, Parkville, Victoria, 3052, Australia.
Kelly
J M
JM
Davis
M A
MA
Hynes
M J
MJ
D000085:Acetates / Q000378:metabolism*; D000483:Alleles; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D004790:Enzyme Induction; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis / Q000378:metabolism; D005800:Genes, Fungal / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics* / Q000502:physiology; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics; D013696:Temperature; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D016335:Zinc Fingers
D000085:Acetates; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D000581:Amidohydrolases; C021445:acetamidase