Alban C
Laboratoire mixte CNRS-Aventis (UMR1932 associée au CNRS), Aventis CropScience, Lyon, France.
C R Acad Sci III. 2000 Aug;323(8):681-8. doi: 10.1016/s0764-4469(00)01223-3.
Holocarboxylase synthetases (HCSs) catalyse the biotinylation of biotin-dependent carboxylases in both prokaryotes and eukaryotes. In Escherichia coli and Bacillus subtilis, the protein also acts as a transcriptional repressor that regulates the synthesis of biotin. Previously, we isolated and characterized a cDNA encoding an Arabidopsis thaliana HCS and subsequently assigned this enzyme form to the chloroplast compartment. To investigate whether or not the Arabidopsis protein may function as a regulator in E. coli, we have expressed the functional plant HCS in a birA-derepressed mutant strain of E. coli devoid of the corresponding E. coli protein and carrying a promoter-less LacZ gene marker inserted into the biotin operon, such that the bio promoter drives the synthesis of beta-galactosidase. Our data demonstrate that although the expressed plant HCS efficiently complemented the function of apo-carboxylase biotinylation in E. coli, it proved unable to regulate the expression of the biotin biosynthetic genes.
全羧化酶合成酶（HCSs）在原核生物和真核生物中催化生物素依赖性羧化酶的生物素化。在大肠杆菌和枯草芽孢杆菌中，该蛋白质还作为转录阻遏物调节生物素的合成。此前，我们分离并鉴定了拟南芥HCS的编码cDNA，随后将这种酶形式定位到叶绿体区室。为了研究拟南芥蛋白是否可能在大肠杆菌中发挥调节作用，我们在大肠杆菌的birA去阻遏突变株中表达了功能性植物HCS，该突变株缺乏相应的大肠杆菌蛋白，并在生物素操纵子中插入了一个无启动子的LacZ基因标记，使得生物启动子驱动β-半乳糖苷酶的合成。我们的数据表明，尽管表达的植物HCS有效地补充了大肠杆菌中脱辅基羧化酶生物素化的功能，但它无法调节生物素生物合成基因的表达。
