Uria-Nickelsen M R, Leadbetter E R, Godchaux W
Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269-2131.
FEMS Microbiol Lett. 1994 Oct 15;123(1-2):43-8. doi: 10.1111/j.1574-6968.1994.tb07199.x.
Strains of Escherichia coli lacking serine transacetylase or a positive regulator (Cys B protein) of the assimilatory sulfate reduction (ASR) pathway were unable to assimilate sulfonate-S, while single mutants in O-acetyl-L-serine sulfhydrylase (either 'A' or 'B') were able to do so. Mutants unable to reduce sulfate to sulfite were nonetheless able to form and accumulate sulfide and then cysteine from sulfonates, while strains lacking sulfite reductase were not. Thus terminal portions of the ASR pathway are involved in reduction of sulfonate-S to that of cysteine. E. coli K-12 formed cysteine more slowly, and accumulated lesser amounts of it with sulfonate-sulfur than it did from either sulfate or sulfite. These observations are consistent with our earlier report that sulfate is the preferred sulfur source when present simultaneously with a sulfonate.
缺乏丝氨酸转乙酰酶或同化性硫酸盐还原（ASR）途径的正调控因子（Cys B蛋白）的大肠杆菌菌株无法同化磺酸盐-S，而O-乙酰-L-丝氨酸巯基酶（“A”或“B”）的单突变体则能够同化。无法将硫酸盐还原为亚硫酸盐的突变体仍然能够从磺酸盐中形成并积累硫化物，进而形成半胱氨酸，而缺乏亚硫酸盐还原酶的菌株则不能。因此，ASR途径的末端部分参与了将磺酸盐-S还原为半胱氨酸的过程。与从硫酸盐或亚硫酸盐相比，大肠杆菌K-12利用磺酸盐硫形成半胱氨酸的速度更慢，积累的量也更少。这些观察结果与我们之前的报告一致，即当硫酸盐与磺酸盐同时存在时，硫酸盐是首选的硫源。
