Brady R A, Csonka L N
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
J Bacteriol. 1988 May;170(5):2379-82. doi: 10.1128/jb.170.5.2379-2382.1988.
We found that the expression of beta-galactosidase in Salmonella typhimurium strains carrying proC-lacZ fusions was neither repressed by excess proline nor derepressed by proline limitation. Except for a three- to fourfold decrease in the beta-galactosidase specific activity under conditions causing a severely reduced growth rate, the expression of the proC-lacZ fusions was nearly invariant under a variety of culture conditions. Thus, the proC gene is unlike most other amino acid biosynthetic genes in that its expression is nearly constitutive.
我们发现,携带proC-lacZ融合基因的鼠伤寒沙门氏菌菌株中β-半乳糖苷酶的表达既不会因脯氨酸过量而受到抑制,也不会因脯氨酸限制而解除抑制。除了在导致生长速率严重降低的条件下β-半乳糖苷酶比活性下降三到四倍外,proC-lacZ融合基因的表达在各种培养条件下几乎保持不变。因此,proC基因与大多数其他氨基酸生物合成基因不同,其表达几乎是组成型的。