Brangulis Kalvis, Tupina Dagnija, Sinicina Everita Elina, Zelencova-Gopejenko Diana, Akopjana Inara, Bogans Janis, Tars Kaspars
Latvian Biomedical Research and Study Centre, Ratsupites 1 K-1, Riga, 1067, Latvia.
Latvian Institute of Organic Synthesis, Riga, Latvia.
Sci Rep. 2025 Apr 3;15(1):11518. doi: 10.1038/s41598-025-93944-z.
Lyme disease, caused by the spirochete Borrelia burgdorferi, is transmitted to mammalian hosts during the feeding process of infected Ixodes ticks. Our previous studies demonstrated that the paralogous gene family 12 (PFam12) consisting of five members (BBK01, BBG01, BBH37, BBJ08, and BB0844) are non-specific DNA-binding proteins. PFam12 proteins share 31-69% sequence identity, are located either on the surface or within the periplasm and are upregulated as the tick starts its blood meal. The crystal structure of BBK01 revealed that the protein forms a homodimer, which is potentially critical for DNA binding. In this study, we determined the crystal structure of another PFam12 member, BBH37, to gain a better insight into this unique paralogous family. Although BBK01 dimerization is mediated by its C-terminal region and is thought to be critical for DNA binding, BBH37 forms dimers through an alternative mechanism where a unique disulfide bond is involved. We found that BBH37 is still able to interact with DNA with micromolar affinity. Molecular dynamics simulations and site-directed mutagenesis was conducted to characterize these unique DNA binding proteins. This study highlights the structural diversity within the PFam12, demonstrating that despite significant differences in dimerization mechanisms, these proteins retain their DNA-binding capability.
莱姆病由螺旋体伯氏疏螺旋体引起，在受感染的硬蜱进食过程中传播给哺乳动物宿主。我们之前的研究表明，由五个成员（BBK01、BBG01、BBH37、BBJ08和BB0844）组成的旁系同源基因家族12（PFam12）是非特异性DNA结合蛋白。PFam12蛋白的序列同一性为31%-69%，位于表面或周质内，并且在蜱开始吸血时上调。BBK01的晶体结构显示该蛋白形成同二聚体，这可能对DNA结合至关重要。在本研究中，我们确定了另一个PFam12成员BBH37的晶体结构，以更好地了解这个独特的旁系同源家族。尽管BBK01的二聚化由其C末端区域介导，并且被认为对DNA结合至关重要，但BBH37通过涉及独特二硫键的另一种机制形成二聚体。我们发现BBH37仍然能够以微摩尔亲和力与DNA相互作用。进行了分子动力学模拟和定点诱变以表征这些独特的DNA结合蛋白。这项研究突出了PFam12内的结构多样性，表明尽管二聚化机制存在显著差异，但这些蛋白仍保留其DNA结合能力。
