THYMIDINE UPTAKE AND UTILIZATION IN ESCHERICHIA-COLI - NEW GENE CONTROLLING NUCLEOSIDE TRANSPORT
THYMIDINE UPTAKE AND UTILIZATION IN ESCHERICHIA-COLI - NEW GENE CONTROLLING NUCLEOSIDE TRANSPORT
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DOI：
10.1128/jb.126.2.814-822.1976
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发表时间：
1976-01-01
影响因子：
3.2
通讯作者：
HANAWALT, P
中科院分区：
文献类型：
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作者：
MCKEOWN, M;KAHN, M;HANAWALT, P
一种常用的E.大肠杆菌K-12缺乏包括胸苷在内的许多核苷的转运。胸腺嘧啶掺入未受影响。菌株AB 2497在低胸苷浓度（< 1 μ g/ml）下比许多其它菌株表现出显著更低的胸苷脉冲标记掺入。这种缺陷似乎是由于单个基因的突变造成的。该基因命名为nup（用于核苷摄取），位于E. coli连锁图谱。在nup+菌株中，给定核苷的转运对大量过量的其他核苷相对不敏感，但被相同核苷竞争性抑制。缺乏胸苷激酶的突变体缺乏胸苷摄取，但脱氧腺苷摄取正常。提出了一个核苷转运的两步模型，其中第一步利用nup基因产物，是核苷向细胞内部的非特异性转运。在第二步中，通过细胞酶（例如，核苷激酶）以促进积累。
A commonly used strain of E. coli K-12 was deficient in the transport of a number of nucleosides, including thymidine. Thymine incorporation was unaffected. Strain AB2497 exhibited a strikingly lower thymidine pulse-label incorporation at low (< 1 .mu.g/ml) thymidine concentrations than do many other strains. The deficiency appeared to be due to mutation in a single gene. This gene, designated nup (for nucleoside uptake), is located at 10-13 min on the E. coli linkage map. In nup+ strains, the transport of a given nucleoside was relatively insensitive to large excesses of other nucleosides but was competitively inhibited by the same nucleoside. Mutants deficient in thymidine kinase are deficient in thymidine uptake but normal in deoxyadenosine uptake. A 2 step model for nucleoside transport is presented in which the 1st step, utilizing the nup gene product, is a nonspecific translocation of nucleoside to the interior of the cell. In the 2nd step, the individual nucleosides are modified by cellular enzymes (e.g., nucleoside kinases) to facilitate accumulation.