The structural gene encoding S-adenosyl-L-methionine synthetase (SAM-S
) in the fungus Ascobolus immersus has been cloned and sequenced. It c
ontains a 1179-bp ORF, interrupted by three introns, encoding a 393-am
ino-acid protein (42978 Da) that is 90% homologous to the SAM-S of the
filamentous fungus Neurospora crassa, indicating that these fungi are
closely related species.