Role of the murein precursor UDP-N-acetylmuramyl-L-Ala-gamma-D-Glu-meso-diaminopimelic acid-D-Ala-D-Ala in repression of beta-lactamase induction in cell division mutants.
Role of the murein precursor UDP-N-acetylmuramyl-L-Ala-gamma-D-Glu-meso-diaminopimelic acid-D-Ala-D-Ala in repression of beta-lactamase induction in cell division mutants.
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胞壁蛋白前体 UDP-N-乙酰胞壁酰-L-Ala-gamma-D-Glu-meso-二氨基庚二酸-D-Ala-D-Ala 在抑制细胞分裂突变体中 β-内酰胺酶诱导中的作用。
DOI：
10.1128/jb.184.15.4233-4239.2002
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发表时间：
2002
影响因子：
3.2
通讯作者：
Park,JamesT
中科院分区：
文献类型：
--
作者：
Uehara,Tsuyoshi;Park,JamesT
某些β-内酰胺类抗生素可诱导许多革兰氏阴性菌的染色体ampc β-内酰胺酶。天然诱导剂虽然尚未明确确定，但它是一种细胞壁分解产物，通过蛋白循环途径的AmpG渗透酶成分进入细胞。令人惊讶的是，据报道，在缺乏细胞分裂所需的FtsZ或缺乏细胞延伸所需的青霉素结合蛋白2 （PBP2）时，头孢西丁不会诱导β-内酰胺酶。由于这些结果仍未得到解释，我们检测了抗ftsz突变体和其他细胞分裂突变体（ftsA，ftsQ和ftsi）和PBP2突变体诱导β-内酰胺酶。在所有突变体中，β-内酰胺酶未被头孢西丁诱导，这证实了最初的报道。鼠蛋白前体，udp - n -乙酰muramyl-l- ala -γ-d-Glu-meso-diaminopimelic acid-d-Ala-d-Ala (UDP-MurNAc-pentapeptide)，已被证明作为AmpR的协同抑制因子，在体外抑制β-内酰胺酶的表达。我们的研究结果表明，β-内酰胺酶不会被诱导，因为诱导剂无法取代的突变体含有大量的辅抑制因子。在PBP2（Ts）突变体中，除了协同抑制因子的积累外，细胞壁的周转和再循环也大大减少，因此很少或没有诱导剂可用。因此，在这两种情况下，阻遏物与诱导剂的高比例可能会阻止诱导。
Certain β-lactam antibiotics induce the chromosomalampCβ-lactamase of many gram-negative bacteria. The natural inducer, though not yet unequivocally identified, is a cell wall breakdown product which enters the cell via the AmpG permease component of the murein recycling pathway. Surprisingly, it has been reported that β-lactamase is not induced by cefoxitin in the absence of FtsZ, which is required for cell division, or in the absence of penicillin-binding protein 2 (PBP2), which is required for cell elongation. Since these results remain unexplained, we examined anftsZmutant and other cell division mutants (ftsA,ftsQ, andftsI) and a PBP2 mutant for induction of β-lactamase. In all mutants, β-lactamase was not induced by cefoxitin, which confirms the initial reports. The murein precursor, UDP-N-acetylmuramyl-l-Ala-γ-d-Glu-meso-diaminopimelic acid-d-Ala-d-Ala (UDP-MurNAc-pentapeptide), has been shown to serve as a corepressor with AmpR to repress β-lactamase expression in vitro. Our results suggest that β-lactamase is not induced because theftsmutants contain a greatly increased amount of corepressor which the inducer cannot displace. In the PBP2(Ts) mutant, in addition to accumulation of corepressor, cell wall turnover and recycling were greatly reduced so that little or no inducer was available. Hence, in both cases, a high ratio of repressor to inducer presumably prevents induction.