Piras G, el Kharroubi A, van Beeumen J, Coeme E, Coyette J, Ghuysen J M
Service de Microbiologie, Université de Liège, Sart Tilman, Belgium.
J Bacteriol. 1990 Dec;172(12):6856-62. doi: 10.1128/jb.172.12.6856-6862.1990.
Enterococcus hirae S185, a clinical isolate from swine intestine, exhibits a relatively high resistance to penicillin and contains two 77-kDa penicillin-binding proteins 3 of high (PBP 3s) and low (PBP 3r) affinity to penicillin, respectively. A laboratory mutant S185r has been obtained which overproduces PBP 3r and has a highly increased resistance to penicillin. Peptide fragments specifically produced by trypsin and SV8 protease digestions of PBP 3r were isolated, and the amino acid sequences of their amino terminal regions were determined. On the basis of these sequences, oligonucleotides were synthesized and used as primers to generate, by polymerization chain reaction, a 233-bp DNA fragment the sequence of which translated into a 73-amino-acid peptide segment of PBP 3r. These structural data led to the conclusion that the E. hirae PBP 3r and the methicillin-resistant staphylococcal PBP 2' are members of the same class of high-Mr PBPs. As shown by immunological tests, PBP 3r is not related to PBP 3s but, in contrast, is related to the 71-kDa PBP 5 of low penicillin affinity which is responsible for penicillin resistance in E. hirae ATCC 9790 and R40.
平肠球菌S185是一株从猪肠道分离出的临床菌株，对青霉素表现出相对较高的抗性，并且含有两种分别对青霉素具有高亲和力（PBP 3s）和低亲和力（PBP 3r）的77-kDa青霉素结合蛋白3。已获得一株实验室突变体S185r，它过量表达PBP 3r并且对青霉素的抗性大幅增加。分离了通过胰蛋白酶和SV8蛋白酶消化PBP 3r特异性产生的肽片段，并确定了其氨基末端区域的氨基酸序列。基于这些序列，合成了寡核苷酸并用作引物，通过聚合酶链反应产生了一个233-bp的DNA片段，其序列翻译成PBP 3r的一个73个氨基酸的肽段。这些结构数据得出结论，平肠球菌PBP 3r和耐甲氧西林葡萄球菌的PBP 2'属于同一类高分子量青霉素结合蛋白。免疫测试表明，PBP 3r与PBP 3s无关，相反，它与低青霉素亲和力的71-kDa PBP 5相关，该蛋白负责平肠球菌ATCC 9790和R40中的青霉素抗性。
