Clarke S, Koshland D E
J Biol Chem. 1979 Oct 10;254(19):9695-702.
High affinity binding sites for serine and aspartate have been characterized in membranes from Salmonella typhimurium and Escherichia coli. Greater than 80% of these sites have been identified as chemotaxis receptors. Mutants lacking binding sites for these amino acids have been shown to have corresponding defects in taxis. The substrate specificity of each of the receptors in Salmonella is very high; most analogs of serine and aspartate do not bind to these receptor sites and do not affect chemotaxis. The transport of these amino acids is apparently not related to chemotaxis. At least 2500 serine receptors and 1200 aspartate receptors with dissociation constants of about 5 microM are present in the membrane fraction of logarithmically growing cells.
在鼠伤寒沙门氏菌和大肠杆菌的细胞膜中已鉴定出丝氨酸和天冬氨酸的高亲和力结合位点。这些位点中超过80%已被确定为趋化性受体。已证明缺乏这些氨基酸结合位点的突变体在趋化性方面存在相应缺陷。沙门氏菌中每种受体的底物特异性都非常高；丝氨酸和天冬氨酸的大多数类似物都不与这些受体位点结合，也不影响趋化性。这些氨基酸的转运显然与趋化性无关。对数生长期细胞的膜部分中存在至少2500个解离常数约为5 microM的丝氨酸受体和1200个天冬氨酸受体。
