Zijderveld C A, Waisfisz Q, Aarsman M E, Nanninga N
Section of Molecular Cytology, BioCentrum Amsterdam, University of Amsterdam, The Netherlands.
J Bacteriol. 1995 Nov;177(21):6290-3. doi: 10.1128/jb.177.21.6290-6293.1995.
The construction of hybrid proteins of PBP1B and PBP3 has been described. One hybrid protein (PBP1B/3) contained the transglycosylase domain of PBP1B and the transpeptidase domain of PBP3. In the other hybrid protein, the putative transglycosylase domain of PBP3 was coupled to the transpeptidase domain of PBP1B (PBP3/1B). The hybrid proteins were localized in the cell envelope in a similar way as the wild-type PBP1B. In vitro isolates of the strains containing the hybrid proteins had a transglycosylase activity intermediate between that of wild-type PBP1B-producing strain and that of a PBP1B overproducer. Analysis with specific antibiotics against PBP1A/1B and PBP3 and mutant analysis in strains containing PBP3/1B revealed no detectable effects in vivo compared with wild-type strains. The same was shown for PBP1B/3 when the experiments were performed in a recA background. The data indicate that the hybrid proteins cannot replace native penicillin-binding proteins. This finding suggests that functional high-molecular-weight penicillin-binding protein specificity is at least in part determined by the unique combination of the two functional domains.
PBP1B和PBP3杂合蛋白的构建方法已被描述。一种杂合蛋白（PBP1B/3）包含PBP1B的转糖基酶结构域和PBP3的转肽酶结构域。在另一种杂合蛋白中，PBP3假定的转糖基酶结构域与PBP1B的转肽酶结构域相连（PBP3/1B）。杂合蛋白定位于细胞膜，定位方式与野生型PBP1B相似。含有杂合蛋白的菌株的体外分离物具有的转糖基酶活性介于产生野生型PBP1B的菌株和过量产生PBP1B的菌株之间。用针对PBP1A/1B和PBP3的特异性抗生素进行分析以及对含有PBP3/1B的菌株进行突变分析，结果显示与野生型菌株相比，体内未检测到影响。当在recA背景下进行实验时，PBP1B/3也得到了同样的结果。数据表明杂合蛋白不能替代天然青霉素结合蛋白。这一发现表明，功能性高分子量青霉素结合蛋白的特异性至少部分由两个功能结构域的独特组合决定。
