过量表达的枯草芽孢杆菌苯丙氨酰 - tRNA合成酶的动力学特性不利于其在体内被赭曲霉毒素A抑制。

Kinetic properties of pure overproduced Bacillus subtilis phenylalanyl-tRNA synthetase do not favour its in vivo inhibition by ochratoxin A.

作者信息

Roth A, Eriani G, Dirheimer G, Gangloff J

机构信息

Institut de Biologie Moléculaire et Cellulaire du CNRS, 15, Strasbourg, France.

出版信息

FEBS Lett. 1993 Jul 12;326(1-3):87-91. doi: 10.1016/0014-5793(93)81767-t.

DOI:10.1016/0014-5793(93)81767-t

PMID:8325392

Abstract

Ochratoxine A (OTA) inhibits growth of Bacillus subtilis at pHs below 7. Since OTA is a phenylalanine analogue, this effect could be due to inhibition of phenylalanine-tRNA synthetase (PheRS) by competition of this mycotoxin with the amino acid. Homogeneous PheRS was purified from Bacillus subtilis and from E. coli transformed with the PheRS gene. The latter produced about 40 times more PheRS than B. subtilis. The Km and Ki values of PheRS, respectively, for phenylalanine and OTA were measured and their concentrations within the cell determined. It appears that the concentration of OTA in the cell, in spite of a 25-fold accumulation, remained too low to significantly compete with phenylalanine. This does not suggest PheRS to be the target of OTA in cell growth and protein synthesis inhibition in Bacillus subtilis. It was also shown that the 2-3-fold increase of PheRS in OTA-treated cells is not due to phenylalanine-controlled attenuation regulation.

摘要

赭曲霉毒素A（OTA）在pH值低于7时会抑制枯草芽孢杆菌的生长。由于OTA是苯丙氨酸类似物，这种作用可能是由于这种霉菌毒素与氨基酸竞争，从而抑制了苯丙氨酸 - tRNA合成酶（PheRS）。从枯草芽孢杆菌和用PheRS基因转化的大肠杆菌中纯化出了均一的PheRS。后者产生的PheRS比枯草芽孢杆菌多约40倍。测定了PheRS对苯丙氨酸和OTA的Km值和Ki值，并确定了它们在细胞内的浓度。尽管细胞内OTA有25倍的积累，但似乎其浓度仍然过低，无法与苯丙氨酸进行有效竞争。这并不表明PheRS是OTA在枯草芽孢杆菌细胞生长和蛋白质合成抑制中的作用靶点。研究还表明，经OTA处理的细胞中PheRS增加2 - 3倍并非由于苯丙氨酸控制的衰减调节。