METHIONINE TRANSPORT IN ESCHERICHIA-COLI - PHYSIOLOGICAL AND GENETIC EVIDENCE FOR 2 UPTAKE SYSTEMS
METHIONINE TRANSPORT IN ESCHERICHIA-COLI - PHYSIOLOGICAL AND GENETIC EVIDENCE FOR 2 UPTAKE SYSTEMS
复制标题
DOI：
10.1128/jb.119.2.401-409.1974
复制
发表时间：
1974-01-01
影响因子：
3.2
通讯作者：
WATSON, WJ
中科院分区：
文献类型：
--
作者：
KADNER, RJ;WATSON, WJ
至少有两个运输系统用于l-蛋氨酸进入大肠杆菌。其中一个系统对蛋氨酸有很高的亲和力(KT约为10−7M)，并被甲硫酰多肽抑制。另一种体系亲和力较低(KTof 40μM)。突变株缺乏高亲和力系统，不能利用蛋氨酸或乙酰蛋氨酸作为蛋氨酸来源。分离到一个突变体，它不仅缺乏高亲和力系统，而且表现出低亲和力系统的活性降低。测定了该菌株中残存活性的转运参数。运输的能量来源似乎与亲本菌株相同。转运活动的丧失并没有伴随蛋氨酸池大小或蛋氨酸排泄或合成速度的重大变化。对回复突变体和转导杂交的分析支持这样的结论：所描述的菌株是metthD(编码高亲和力系统)和metP(低亲和力系统)的双重突变体。该基因座位于A(38%共转导)和ProA(9%共转导)之间。
At least two transport systems serve for the entry ofl-methionine intoEscherichia coli. One of these systems has a high affinity for methionine (KTof about 10−7M) and is inhibited by methionyl peptides. The other system has a lower affinity (KTof 40 μM). Mutants defective inmetDlack the high-affinity system and are unable to utilized-methionine orN-acetylmethionine as methionine sources. A mutant was isolated which not only lacks the high-affinity system, but which also exhibits decreased activity of the low-affinity system. The transport parameters of the activity remaining in this strain were measured. The energy source for transport appears to be the same as that in the parental strain. The loss of the transport activities was not accompanied by major changes in the methionine pool size or in the rate of methionine excretion or synthesis. The analysis of revertants and transduction crosses supports the conclusion that the strain described is a double mutant in bothmetD(which codes for the high-affinity system) andmetP(the low-affinity system). ThemetDlocus was found to lie betweentonA(38% co-transduction) andproA(9% co-transduction).