Braun V, Wolff H
J Bacteriol. 1975 Sep;123(3):888-97. doi: 10.1128/jb.123.3.888-897.1975.
In vivo studies on the attachment of lipoprotein to the murein (peptidoglycan) of Escherichia coli showed that it takes several generations of growth until the amount of lipoprotein on newly made murein is equilibrated. The technique used involves degradation of the sodium dodecyl sulfate-insoluble murein-lipoprotein complex (sacculus, rigid layer) with lysozyme and separation of the labeled products on paper. No lipoprotein was found on murein subunits incorporated during a pulse of [3H]diaminopimelate for 1 min in logarithmically growing cells at 37 C. Even after one doubling of the cell mass, only 4 to 8% of the labeled murein was isolated as bound to lipoprotein. With uniformly labeled murein, 30% remains bound to lipoprotein after lysozyme treatment, corresponding to three murein subunits. Therefore it can be concluded that during pulse labeling either no lipoprotein is incorporated into the newly synthesized murein or no murein subunits are inserted into existing murein around lipoprotein attachment sites. Longer pulse and pulse-chase experiments argue for the latter interpretation. It is therefore concluded that incorporation of murein subunits into the growing murein polymer is not at all a random process. Instead, quite large areas of murein, on which lipoprotein is situated, seem to be preserved. Under the influence of penicillin FL 1060 murein synthesis is 50% inhibited. The rate of lipoprotein attachment is less affected so that increasing amounts of lipoprotein become attached during spheroplast formation. By the time the stationary growth phase has been reached, the lipoprotein content of the murein has doubled. Diaminopimelate auxotrophic mutants require, in the presence of penicillin FL 1060, more diaminopimelate for full growth than in the absence of penicillin FL 1060. This finding and the fact that murein synthesis is always inhibited by 50% over a wide range of penicillin concentration (1 to 1,000 mug/ml) point to the inhibition of an enzymatic step of murein synthesis which can be partially bypassed by a second enzyme, less efficient but resistant to penicillin FL 1060.
对脂蛋白与大肠杆菌胞壁质（肽聚糖）结合的体内研究表明，需要经过几代生长，新合成的胞壁质上的脂蛋白量才能达到平衡。所使用的技术包括用溶菌酶降解十二烷基硫酸钠不溶性胞壁质 - 脂蛋白复合物（细胞壁，刚性层），并在纸上分离标记产物。在37℃对数生长期的细胞中，用[3H]二氨基庚二酸脉冲标记1分钟期间掺入的胞壁质亚基上未发现脂蛋白。即使细胞质量加倍一次后，只有4%至8%的标记胞壁质被分离为与脂蛋白结合。对于均匀标记的胞壁质，溶菌酶处理后30%仍与脂蛋白结合，相当于三个胞壁质亚基。因此可以得出结论，在脉冲标记期间，要么没有脂蛋白掺入新合成的胞壁质中，要么没有胞壁质亚基插入脂蛋白附着位点周围现有的胞壁质中。更长时间的脉冲和脉冲追踪实验支持后一种解释。因此可以得出结论，将胞壁质亚基掺入生长的胞壁质聚合物中根本不是一个随机过程。相反，位于其上的脂蛋白的相当大区域的胞壁质似乎得以保留。在青霉素FL 1060的影响下，胞壁质合成被抑制50%。脂蛋白附着速率受影响较小，因此在原生质球形成过程中附着的脂蛋白量增加。到达到稳定生长期时，胞壁质的脂蛋白含量已加倍。在存在青霉素FL 1060的情况下，二氨基庚二酸营养缺陷型突变体比在不存在青霉素FL 1060时需要更多的二氨基庚二酸才能完全生长。这一发现以及胞壁质合成在广泛的青霉素浓度范围（1至1000微克/毫升）内总是被抑制50%这一事实表明，胞壁质合成的一个酶促步骤受到抑制，而第二个酶可以部分绕过这一步骤，该酶效率较低但对青霉素FL 1060有抗性。
