Davis R H, Mora J
J Bacteriol. 1968 Aug;96(2):383-8. doi: 10.1128/jb.96.2.383-388.1968.
The arg-12(s) mutation of Neurospora causes a partial block in the ornithine transcarbamylase (OTC) reaction. Strains carrying this mutation will use endogenous ornithine, but not exogenous ornithine, as a precursor of arginine. Certain strains carrying arg-12(s) may be used for direct selection of variants able to use exogenous ornithine as an arginine precursor. Among eight such derivatives, six lacked the catabolic enzyme ornithine transaminase (OTA). All six mutations were alleles of a single gene, designated ota, on linkage group III. No mutation affected arginase, the first enzyme in the catabolic pathway with OTA. Strains carrying ota mutations alone are vigorous prototrophs, but, unlike wild-type Neurospora, fail to use ornithine efficiently as a sole nitrogen source. The selection method by which ota mutants arose suggests that OTA is severely competitive with OTC for exogeneous ornithine.
粗糙脉孢菌的arg-12(s)突变会导致鸟氨酸转氨甲酰酶（OTC）反应出现部分阻断。携带此突变的菌株会以内源性鸟氨酸而非外源性鸟氨酸作为精氨酸的前体。某些携带arg-12(s)的菌株可用于直接筛选能够利用外源性鸟氨酸作为精氨酸前体的变体。在八个这样的衍生物中，六个缺乏分解代谢酶鸟氨酸转氨酶（OTA）。所有六个突变都是连锁群III上一个名为ota的单一基因的等位基因。没有突变影响精氨酸酶，即与OTA在分解代谢途径中的第一种酶。仅携带ota突变的菌株是活力旺盛的原养型，但与野生型粗糙脉孢菌不同，它们不能有效地将鸟氨酸用作唯一氮源。ota突变体产生的选择方法表明，OTA与OTC在外源性鸟氨酸方面存在严重竞争。
