Methionine synthesis in Neurospora crassa

Abstract

Resting cells of both wild-type and mutant strain no. 34486 of Neurospora crassa form methionine from homocysteine. Formate is the most effective of the various C1 precursors examined. Added pteroylgluta-mate has no effect on methionine synthesis by resting cells of the wild-type organism. Leucovorin cannot restore the decrease in synthesis caused by aminopterin. The methionine synthesis obtained by cell-free extracts of Neurospora crassa (wild) is decreased by Dowex 2 (Cl- form) treatment. Addition of heat-inactivated cell-free extracts of either Neurospora crassa or Ochromonas malhamensis, or a cofactor mixture consisting of adenosine triphosphate, diphosphopyridine nucleotide, magnesium sulphate and leucovorin, partially restores the activity.