Escherichia coli mutants impaired in maltodextrin transport
Escherichia coli mutants impaired in maltodextrin transport
复制标题
大肠杆菌突变体麦芽糖糊精转运受损
DOI：
10.1128/jb.140.1.1-13.1979
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发表时间：
1979
影响因子：
3.2
通讯作者：
T. Ferenci
中科院分区：
文献类型：
--
作者：
C. Wandersman;M. Schwartz;T. Ferenci
野生型大肠杆菌K-12在麦芽糖和含有多达7个葡萄糖残基的麦芽糊精上同样生长良好。对三类不能在麦芽糊精上生长，但仍能在麦芽糖上生长的突变体进行了详细的研究。已知的第一类是由抗lambda噬菌体突变体组成，它们缺乏lamb基因编码的外膜蛋白。这些突变体生长在麦芽糖和麦芽三糖上，但完全不能生长在麦芽糖和更长的麦芽糊精上，麦芽糊精不能穿过外膜。第二类突变在男性中受到影响，这是周质麦芽糖结合蛋白的结构基因。从新突变体中分离的麦芽糖结合蛋白在底物结合特性上发生了改变，但改变的方式并不能解释突变的表型。相反，生长实验和运输研究的结果表明，这些雄性突变体通过外膜运输麦芽糊精的能力受到了损害。这意味着麦芽糖结合蛋白(在野生型菌株中)与lambda受体合作，通过外膜渗透。这篇文章中描述的最后一类突变体受到了MalG的影响，或者可能是在一个尚未检测到的靠近MalG的基因中受到影响。它们在麦芽糊精从周质间隙到细胞质的转运过程中存在缺陷，但对麦芽糖的转运只有轻微的影响。
Wild-type Escherichia coli K-12 was found to grow equally well on maltose and on maltodextrins containing up to seven glucose residues. Three classes of mutants unable to grow on maltodextrins, but still able to grow on maltose, were investigated in detail. The first class, already known, was composed of phage lambda-resistant mutants, which lack the outer membrane protein coded by gene lamB. These mutants grow on maltose and maltotriose but not at all on maltotetraose and longer maltodextrins which cannot cross the outer membrane. A second class of mutants were affected in malE, the structural gene of the periplasmic maltose binding protein. The maltose binding proteins isolated from the new mutants were altered in their substrate binding properties, but not in a way that could account for the mutant phenotypes. Rather, the results of growth experiments and transport studies suggest that these malE mutants are impaired in their ability to transport maltodextrins across the outer membrane. This implies that the maltose binding protein (in wild-type strains) cooperates with the lambda receptor in permeation through the outer membrane. The last class of mutants described in this paper were affected in malG, or perhaps in an as yet undetected gene close to malG. They were defective in the transfer of maltodextrins from the periplasmic space to the cytoplasm but only slightly affected in the transport of maltose.