Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824.
Proc Natl Acad Sci U S A. 1987 Dec;84(23):8444-7. doi: 10.1073/pnas.84.23.8444.
Cochliobolus carbonum race 1 produces a cyclic tetrapeptide HC-toxin, which is necessary for its exceptional virulence on certain varieties of maize. Previous genetic analysis of HC-toxin production by the fungus has indicated that a single genetic locus controls HC-toxin production. Enzymes involved in the biosynthesis of HC-toxin have been sought by following the precedents established for the biosynthetic enzymes of cyclic peptide antibiotics. Two enzymatic activities from C. carbonum race 1 were found, a D-alanine- and an L-proline-dependent ATP/PP(i) exchange, which by biochemical and genetic criteria were shown to be involved in the biosynthesis of HC-toxin. These two activities were present in all tested race 1 isolates of C. carbonum, which produce HC-toxin, and in none of the tested race 2 and race 3 isolates, which do not produce the toxin. In a genetic cross between two isolates of C. carbonum differing at the tox locus, all tox(+) progeny had both activities, and all tox(-) progeny lacked both activities.
炭角菌 1 号产生一种环状四肽 HC 毒素,该毒素对于其在某些特定玉米品种上的超强毒性是必需的。之前对真菌产生 HC 毒素的遗传分析表明,单个遗传基因座控制 HC 毒素的产生。通过遵循环状肽抗生素生物合成酶的先例,我们一直在寻找参与 HC 毒素生物合成的酶。从炭角菌 1 号中发现了两种酶活性,一种是 D-丙氨酸和 L-脯氨酸依赖性的 ATP/PP(i)交换,通过生化和遗传标准表明它们参与了 HC 毒素的生物合成。这两种活性存在于所有产生 HC 毒素的炭角菌 1 号测试分离株中,而在不产生毒素的炭角菌 2 号和 3 号测试分离株中则不存在。在两个在 tox 基因座上不同的炭角菌分离株之间的遗传杂交中,所有 tox(+)后代都具有这两种活性,而所有 tox(-)后代都缺乏这两种活性。