Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea; Protein Structure Research Team, Korea Basic Science Institute, 162 Yeongudanji-Ro, Ochang-Eup, Cheongju-Si, Chungcheongbuk-Do 28119, South Korea.
Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, South Korea.
Structure. 2019 Sep 3;27(9):1355-1365.e4. doi: 10.1016/j.str.2019.07.001. Epub 2019 Jul 25.
Phage endolysins are hydrolytic enzymes that cleave the bacterial cell wall during the lytic cycle. We isolated the bacteriophage PBC5 against Bacillus cereus, a major foodborne pathogen, and describe the molecular interaction between endolysin LysPBC5 and the host peptidoglycan structure. LysPBC5 has an N-terminal glycoside hydrolase 25 domain, and a C-terminal cell-wall binding domain (CBD) that is critical for specific cell-wall recognition and lysis. The crystal and solution structures of CBDs reveal tandem SH3b domains that are tightly engaged with each other. The CBD binds to the peptidoglycan in a bidentate manner via distal β sheet motifs with pseudo 2-fold symmetry, which can explain its high affinity and host specificity. The CBD primarily interacts with the glycan strand of the peptidoglycan layer instead of the peptide crosslink, implicating the tertiary structure of peptidoglycan as the recognition motif of endolysins.
噬菌体裂解酶是在裂解周期中水解细菌细胞壁的酶。我们分离出了针对蜡样芽孢杆菌的噬菌体 PBC5，蜡样芽孢杆菌是一种主要的食源性致病菌，并描述了裂解酶 LysPBC5 与宿主肽聚糖结构之间的分子相互作用。LysPBC5 具有一个 N 端糖苷水解酶 25 结构域和一个 C 端细胞壁结合结构域 (CBD)，该结构域对于特定的细胞壁识别和裂解至关重要。CBD 的晶体和溶液结构揭示了彼此紧密结合的串联 SH3b 结构域。CBD 通过具有假 2 重对称的远端 β 片层基序以双齿方式结合到肽聚糖上，这可以解释其高亲和力和宿主特异性。CBD 主要与肽聚糖层的聚糖链相互作用，而不是与肽交联相互作用，这表明肽聚糖的三级结构是裂解酶的识别模体。
