TRANSPORT AND UTILIZATION OF D-METHIONINE AND OTHER METHIONINE SOURCES IN ESCHERICHIA-COLI
TRANSPORT AND UTILIZATION OF D-METHIONINE AND OTHER METHIONINE SOURCES IN ESCHERICHIA-COLI
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DOI：
10.1128/jb.129.1.207-216.1977
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发表时间：
1977-01-01
影响因子：
3.2
通讯作者：
KADNER, RJ
中科院分区：
文献类型：
--
作者：
KADNER, RJ
研究了D-蛋氨酸在几株大肠杆菌中的转运和利用。coli K-12。野生型细胞显示Km为1.16 μ M的单一转运系统。该活性表现出与L-甲硫氨酸摄取相似的特异性。在metD突变株中丧失了对D-异构体的活性和对L-甲硫氨酸的高亲和力摄取，沿着丧失了利用D-甲硫氨酸作为甲硫氨酸源的能力。这两种活性对metD的基因剂量的反应相同，并且在回复突变体或转导突变体中都被恢复。虽然L-甲硫氨酸是D-甲硫氨酸摄取的有效抑制剂，但D-甲硫氨酸对L-异构体的摄取影响很小或没有影响。在筛选中未发现仅对2种异构体中的1种异构体的摄取发生改变的突变体。这两种活动的调节是相似的，在他们的内部蛋氨酸池的反应，和证据表明，这些活动的部分抑制控制。证据是最一致的metD产品的作用，作为一个共同的步骤2蛋氨酸特异性摄取系统，但其他基因产品可能代表的初始底物结合位点。该系统也可能参与N-乙酰甲硫氨酸和甲硫氨酸亚砜和甲硫氨酸亚砜亚胺的摄取。甲硫氨酸的酮类似物α-甲硫氨酸的摄取酮-γ-甲基丁酸酯，可以由特异于α-甲基丁酸酯的单独系统介导。长度为5-6个C单元的酮酸直链酸。
The transport and utilization of D-methionine was investigated in several strains of E. coli K-12. Wild-type cells exhibit a single transport system with a Km of 1.16 .mu.M. This activity exhibits a specificity similar to that of the uptake of L-methionine. The activity toward the D-isomer and the high-affinity uptake of L-methionine are lost in strains mutant in metD, along with the ability to utilize D-methionine as methionine source. Both activities respond identically to gene dosage of metD and are both restored in revertants or transductants. Although L-methionine is a potent inhibitor of D-methionine uptake, D-methionine has little or no effect on the uptake of the L-isomer. No mutants altered in the uptake of only 1 of the 2 isomers were found in a screening. Regulation of both activities was similar in their response to the internal methionine pool, and evidence indicates partial repressive control of these activities. The evidence is most consistent with the role of the metD product as a common step for 2 methionine-specific uptake systems, but other gene products may represent the initial substrate binding sites. This system also may be involved in the uptake of N-acetyl methionine and methionine sulfoxide and methionine sulfoximine. The uptake of the keto analog of methionine, .alpha.-keto-.gamma.-methiol butyrate, may be mediated by a separate system specific for .alpha.-keto straight-chain acids 5-6 C units in length.