Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA.
National Institute of Immunology, New Delhi, India.
Nat Commun. 2023 Jul 17;14(1):4268. doi: 10.1038/s41467-023-39966-5.
Penicillin-binding proteins (PBPs) are essential for the formation of the bacterial cell wall. They are also the targets of β-lactam antibiotics. In Enterococcus faecium, high levels of resistance to β-lactams are associated with the expression of PBP5, with higher levels of resistance associated with distinct PBP5 variants. To define the molecular mechanism of PBP5-mediated resistance we leveraged biomolecular NMR spectroscopy of PBP5 - due to its size (>70 kDa) a challenging NMR target. Our data show that resistant PBP5 variants show significantly increased dynamics either alone or upon formation of the acyl-enzyme inhibitor complex. Furthermore, these variants also exhibit increased acyl-enzyme hydrolysis. Thus, reducing sidechain bulkiness and expanding surface loops results in increased dynamics that facilitates acyl-enzyme hydrolysis and, via increased β-lactam antibiotic turnover, facilitates β-lactam resistance. Together, these data provide the molecular basis of resistance of clinical E. faecium PBP5 variants, results that are likely applicable to the PBP family.
青霉素结合蛋白（PBPs）是细菌细胞壁形成所必需的。它们也是β-内酰胺类抗生素的作用靶点。在屎肠球菌中，高水平的β-内酰胺类抗生素耐药性与 PBP5 的表达有关，而更高水平的耐药性与不同的 PBP5 变体有关。为了定义 PBP5 介导的耐药性的分子机制，我们利用了生物分子 NMR 光谱学研究 PBP5-由于其大小（>70 kDa），这是一个具有挑战性的 NMR 靶标。我们的数据表明，耐药性的 PBP5 变体单独或在形成酰基-酶抑制剂复合物时表现出明显增加的动力学。此外，这些变体也表现出增加的酰-酶水解。因此，减少侧链的庞大性和扩展表面环会增加动力学，从而促进酰-酶水解，并通过增加β-内酰胺类抗生素的周转率，促进β-内酰胺类抗生素的耐药性。这些数据共同提供了临床屎肠球菌 PBP5 变体耐药性的分子基础，这些结果可能适用于 PBP 家族。
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