The cyclic peptide synthetase catalyzing HC-toxin production in the filamentous fungus Cochliobolus carbonum is encoded by a 15.7-kilobase open reading frame

J Biol Chem. 1992 Dec 25;267(36):26044-9.


Race 1 of Cochliobolus carbonum, a fungal plant pathogen, owes its exceptional virulence on certain genotypes of maize to the production of HC-toxin, a cyclic tetrapeptide. Production of HC-toxin is controlled by a single known gene, TOX2. Race 1, but not races that do not make HC-toxin, contains two copies of a 22-kilobase (kb) region of chromosomal DNA that is required for HC-toxin biosynthesis and hence virulence. We have sequenced this 22-kb region and here show that it contains an open reading frame of 15.7 kb that encodes a multifunctional cyclic peptide synthetase of potential M(r)574,620. This gene, called HTS1, apparently contains no introns. The predicted gene product, HC-toxin synthetase (HTS), contains four amino acid-binding (adenylate-forming) domains that are highly similar to those found in other cyclic peptide synthetases and other adenylate-binding enzymes. The DNA sequence encodes tryptic peptides derived from two HC-toxin biosynthetic enzymes, HC-toxin synthetase 1 (HTS-1) and HC-toxin synthetase 2 (HTS-2), indicating that these two enzymes exist in vivo as part of a single polypeptide. Consistent with this, in some enzyme preparations antibodies against the enzyme HTS-2, which was originally purified as a protein with a subunit M(r) of 160,000, recognize a protein with an estimated subunit M(r) greater than 480,000.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Isomerases*
  • Amino Acid Sequence
  • Ascomycota / enzymology*
  • Ascomycota / genetics*
  • Base Sequence
  • Blotting, Western
  • Chromosomes, Fungal
  • DNA, Fungal / genetics
  • DNA, Fungal / isolation & purification
  • Electrophoresis, Polyacrylamide Gel
  • Genes, Fungal
  • Hydrolases*
  • Isoenzymes / genetics*
  • Molecular Sequence Data
  • Molecular Weight
  • Mycotoxins / biosynthesis*
  • Oligodeoxyribonucleotides
  • Open Reading Frames*
  • Peptide Fragments / isolation & purification
  • Peptide Synthases / genetics*
  • Peptides, Cyclic / biosynthesis*
  • Poly A / genetics
  • Poly A / isolation & purification
  • RNA / genetics
  • RNA / isolation & purification
  • RNA, Messenger
  • Sequence Homology, Amino Acid


  • DNA, Fungal
  • Isoenzymes
  • Mycotoxins
  • Oligodeoxyribonucleotides
  • Peptide Fragments
  • Peptides, Cyclic
  • RNA, Messenger
  • HC-toxin synthetase 1
  • Poly A
  • RNA
  • HC toxin
  • Hydrolases
  • Amino Acid Isomerases
  • HC-toxin synthetase 2
  • Peptide Synthases

Associated data

  • GENBANK/D10520
  • GENBANK/D12749
  • GENBANK/D12750
  • GENBANK/D12751
  • GENBANK/D12752
  • GENBANK/D12753
  • GENBANK/L01441
  • GENBANK/L01792
  • GENBANK/L01793
  • GENBANK/M98024