Clément J M, Lepouce E, Marchal C, Hofnung M
Unité de Programmation Moléculaire et Toxicologie Génétique, CNRS LA 271, INSERM U.163, Institut Pasteur, Paris, France.
EMBO J. 1983;2(1):77-80. doi: 10.1002/j.1460-2075.1983.tb01384.x.
Gene lamB encodes the outer membrane receptor for phage lambda in Escherichia coli K12. We have determined the DNA sequence alterations of 17 lamB point mutations which result in resistance to phage lambda h+. The mutations correspond to four phenotypic classes according to the pattern of growth of three phages which use the lambda receptor: lambda h (a one-step host-range derivative of lambda h+), lambda hh* (a two-step host-range derivative of lambda h+) and K10 (another lambdoid phage). Fourteen mutations are of the missense type and correspond to Gly to Asp changes distributed as follows. One class I mutation is at position 382 of the mature lambda receptor. Seven class I* mutations, four of which at least are independent, are at position 401. Six independent class II mutations are at position 151. The three other (class III) mutations are of the nonsense type. They change codons TGG (Trp) into TAG (amber) at positions 120 (two mutations) and 351 (one mutation). Implications of these results for the topological organization of the lambda receptor as well as possible reasons for the limited number of altered sites detected are discussed.
基因lamB编码大肠杆菌K12中噬菌体λ的外膜受体。我们已经确定了17个lamB点突变的DNA序列改变，这些突变导致对噬菌体λh +产生抗性。根据三种使用λ受体的噬菌体的生长模式，这些突变对应于四个表型类别：λh（λh +的一步宿主范围衍生物）、λhh*（λh +的两步宿主范围衍生物）和K10（另一种类λ噬菌体）。14个突变是错义类型，对应于甘氨酸到天冬氨酸的变化，分布如下。一个I类突变位于成熟λ受体的382位。七个I*类突变，其中至少四个是独立的，位于401位。六个独立的II类突变位于151位。其他三个（III类）突变是无义类型。它们在120位（两个突变）和351位（一个突变）将密码子TGG（色氨酸）变为TAG（琥珀突变）。讨论了这些结果对λ受体拓扑结构的影响以及检测到的改变位点数量有限的可能原因。
