Duplay P, Szmelcman S
Unité de Programmation Moléculaire et Toxicologie Génétique, (CNRS UA271, INSERM U163), Institut Pasteur, Paris, France.
J Mol Biol. 1987 Apr 20;194(4):675-8. doi: 10.1016/0022-2836(87)90244-0.
We examined the chemotactic behavior of ten Escherichia coli mutants able to synthesize a modified periplasmic maltose-binding protein (MBP) retaining high affinity for maltose. Eight were able to grow on maltose (Mal+), two were not (Mal-). In the capillary assay six out of eight of the Mal+ strains showed an optimal response at the same concentration of maltose as the wild-type strain; the amplitude of the response was strongly reduced in two Mal+ mutants and partially affected in one. The amplitude of the chemotactic response of the two Mal- strains was at least equal to that of the wild type, so that the chemotactic and transport functions of MBP were dissociated in these two cases. We define two regions of the protein (residues 297 to 303 and 364 to 369), that are important both for the chemotactic response and for transport, and one region (residues 207 to 220) that is essential for transport but dispensable for chemotaxis. Interestingly, some regions that were found to be inessential for transport are also dispensable for chemotaxis.
我们研究了十种能够合成对麦芽糖保持高亲和力的修饰型周质麦芽糖结合蛋白（MBP）的大肠杆菌突变体的趋化行为。其中八个能够在麦芽糖上生长（Mal+），两个不能（Mal-）。在毛细管试验中，八个Mal+菌株中的六个在与野生型菌株相同的麦芽糖浓度下表现出最佳反应；两个Mal+突变体的反应幅度大幅降低，一个受到部分影响。两个Mal-菌株的趋化反应幅度至少与野生型相等，因此在这两种情况下，MBP的趋化和转运功能是分离的。我们确定了该蛋白的两个区域（第297至303位氨基酸残基和第364至369位氨基酸残基），它们对趋化反应和转运都很重要，还有一个区域（第207至220位氨基酸残基）对转运至关重要，但对趋化作用可有可无。有趣的是，一些被发现对转运不重要的区域对趋化作用也可有可无。
