Perera Yasiru R, Enriquez Kyle T, Rodriguez Aslin, Garcia Velia, Akizuki Tae, Naretto Anais, Togashi Melumo, Guillen Ryan, Skaar Eric P, Chazin Walter J
Departments of Biochemistry and Chemistry, Vanderbilt University, Nashville, Tennessee, USA.
Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA.
Protein Sci. 2025 Oct;34(10):e70294. doi: 10.1002/pro.70294.
Calprotectin (CP) is an S100A8/S100A9 heterodimer that plays an important role in nutritional immunity at the host-microbe interface. CP combats Staphylococcus aureus growth by sequestration of zinc and other trace transition metals; however, questions remain about whether CP antimicrobial activity strictly relies on metal sequestration. Moreover, the precise mechanism for how zinc binds at the two distinct transition metal binding sites of CP is not known. High-resolution X-ray crystal structures reveal tetracoordinate binding in the canonical HisAsp site and hexacoordinate binding in the His site similar to the binding of manganese and nickel in this site. The S100A9 C-terminal extension (tail) contributes two of the His residues in the His metal-binding site, but measurements of zinc affinity show there is no significant reduction upon mutation of these His residues or deletion of the entire C-terminal tail. Bacterial growth and static biofilm assays show that the His mutations affect S. aureus biomass accumulation differently than loss of the S100A9 C-terminal tail, despite resulting in the same defect in bacterial-CP binding. These results reveal that the S100A9 tail of CP has a role in preventing S. aureus biomass accumulation.
钙卫蛋白（CP）是一种S100A8/S100A9异二聚体，在宿主-微生物界面的营养免疫中发挥重要作用。CP通过螯合锌和其他微量过渡金属来对抗金黄色葡萄球菌的生长；然而，关于CP的抗菌活性是否严格依赖于金属螯合仍存在疑问。此外，锌如何在CP的两个不同过渡金属结合位点结合的确切机制尚不清楚。高分辨率X射线晶体结构揭示了在典型的HisAsp位点的四配位结合以及在His位点的六配位结合，类似于该位点中锰和镍的结合。S100A9 C末端延伸（尾部）在His金属结合位点贡献了两个His残基，但锌亲和力测量表明，这些His残基突变或整个C末端尾部缺失后，锌亲和力没有显著降低。细菌生长和静态生物膜试验表明，His突变对金黄色葡萄球菌生物量积累的影响与S100A9 C末端尾部缺失不同，尽管两者导致细菌与CP结合的缺陷相同。这些结果表明，CP的S100A9尾部在防止金黄色葡萄球菌生物量积累方面发挥作用。
