Collier D N, Spence C, Cox M J, Phibbs P V
Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
FEMS Microbiol Lett. 2001 Mar 15;196(2):87-92. doi: 10.1111/j.1574-6968.2001.tb10546.x.
The amiE gene encodes an aliphatic amidase capable of converting fluoroacetamide to the toxic compound fluoroacetate and is one of many genes whose expression is subject to catabolite repression control in Pseudomonas aeruginosa. The protein product of the crc gene, Crc, is required for repression of amiE and most other genes subject to catabolite repression control in this bacterium. When grown in a carbon source such as succinate, wild-type P. aeruginosa is insensitive to fluoroacetamide (due to repression of amiE expression). In contrast, mutants harboring the crc-10 null allele cannot grow in the presence of fluoroacetamide (due to lack of repression of amiE). Selection for succinate-dependent, fluoroacetamide-resistant derivatives of the crc-10 mutant yielded three independent pseudorevertants containing suppressors that restored a degree of catabolite repression control. Synthesis of Crc protein was not reestablished in these pseudorevertants. All three suppressors of crc-10 were extragenic, and all three also suppressed a Delta crc::tetA allele. In each of the three pseudorevertants, catabolite repression control of amidase expression was restored. Catabolite repression control of mannitol dehydrogenase production was also restored in two of the three isolates. None of the suppressors restored repression of glucose-6-phosphate dehydrogenase or pyocyanin production.
amiE基因编码一种脂肪族酰胺酶，该酶能够将氟乙酰胺转化为有毒化合物氟乙酸盐，它是众多在铜绿假单胞菌中其表达受到分解代谢物阻遏控制的基因之一。crc基因的蛋白质产物Crc是抑制amiE以及该细菌中大多数其他受分解代谢物阻遏控制的基因所必需的。当在琥珀酸盐等碳源中生长时，野生型铜绿假单胞菌对氟乙酰胺不敏感（由于amiE表达受到抑制）。相比之下，携带crc - 10无效等位基因的突变体在氟乙酰胺存在的情况下无法生长（由于缺乏对amiE的抑制）。对crc - 10突变体的琥珀酸盐依赖性、氟乙酰胺抗性衍生物进行筛选，得到了三个独立的假回复突变体，其中含有恢复了一定程度分解代谢物阻遏控制的抑制子。在这些假回复突变体中未重新建立Crc蛋白的合成。crc - 10的所有三个抑制子都是基因外的，并且这三个抑制子也抑制了Δcrc::tetA等位基因。在这三个假回复突变体中的每一个中，酰胺酶表达的分解代谢物阻遏控制都得以恢复。在三个分离株中的两个中，甘露醇脱氢酶产生的分解代谢物阻遏控制也得以恢复。没有一个抑制子恢复对6 - 磷酸葡萄糖脱氢酶或绿脓菌素产生的抑制。
