Institute of Biostructures and Bioimaging, CNR, Napoli, Italy.
Department of Pathogen Biology and Immunology, Institute of Genetics and Microbiology, University of Wrocław, Wrocław, Poland.
Structure. 2020 Jun 2;28(6):613-624.e4. doi: 10.1016/j.str.2020.04.015. Epub 2020 May 7.
Capsule polysaccharide is a major virulence factor of Klebsiella pneumoniae, a nosocomial pathogen associated with a wide range of infections. It protects bacteria from harsh environmental conditions, immune system response, and phage infection. To access cell wall-located receptors, some phages possess tailspike depolymerases that degrade the capsular polysaccharide. Here, we present the crystal structure of a tailspike against Klebsiella, KP32gp38, whose primary sequence shares no similarity to other proteins of known structure. In the trimeric structure of KP32gp38, each chain contains a flexible N-terminal domain, a right-handed parallel β helix domain and two β sandwiches with carbohydrate binding features. The crystal structure and activity assays allowed us to locate the catalytic site. Also, our data provide experimental evidence of a branching architecture of depolymerases in KP32 Klebsiella viruses, as KP32gp38 displays nanomolar affinity to another depolymerase from the same phage, KP32gp37. Results provide a structural framework for enzyme engineering to produce serotype-broad-active enzyme complexes against K. pneumoniae.
荚膜多糖是一种主要的毒力因子，与广泛的感染有关，是一种医院获得性病原体。它保护细菌免受恶劣的环境条件、免疫系统反应和噬菌体感染的影响。为了访问位于细胞壁上的受体，一些噬菌体具有尾刺解聚酶，可降解荚膜多糖。在这里，我们展示了一种针对肺炎克雷伯菌的尾刺的晶体结构，即 KP32gp38，其一级序列与其他已知结构的蛋白质没有相似性。在 KP32gp38 的三聚体结构中，每个链包含一个灵活的 N 端结构域、一个右手平行β螺旋结构域和两个具有碳水化合物结合特征的β三明治。晶体结构和活性测定使我们能够定位催化位点。此外，我们的数据提供了实验证据，证明 KP32 肺炎克雷伯菌病毒中的解聚酶具有分支结构，因为 KP32gp38 对同一噬菌体中的另一种解聚酶 KP32gp37 显示出纳摩尔亲和力。结果为针对肺炎克雷伯菌的产生血清型广泛活性酶复合物的酶工程提供了结构框架。
