The pneumococcal serine rich repeat protein (PsrP) is displayed on the surface of Streptococcus pneumoniae with a suggested role in colonization in the human upper respiratory tract. Full-length PsrP is a 4000 residue-long multi-domain protein comprising a positively charged functional binding region (BR) domain for interaction with keratin and extracellular DNA during pneumococcal adhesion and biofilm formation, respectively. The previously determined crystal structure of the BR domain revealed a flat compressed barrel comprising two sides with an extended β-sheet on one side, and another β-sheet that is distorted by loops and β-turns on the other side. Crystallographic B-factors indicated a relatively high mobility of loop regions that were hypothesized to be important for binding. Furthermore, the crystal structure revealed an inter-molecular β-sheet formed between edge strands of two symmetry-related molecules, which could promote bacterial aggregation during biofilm formation. Here we report the near complete ¹⁵N/¹³C/¹H backbone resonance assignment of the BR domain of PsrP, revealing a secondary structure profile that is almost identical to the X-ray structure. Dynamic ¹⁵N-T₁, T₂ and NOE data suggest a monomeric and rigid structure of BR with disordered residues only at the N- and C-termini. The presented peak assignment will allow us to identify BR residues that are crucial for ligand binding.

中文翻译：

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肺炎球菌富含丝氨酸重复蛋白 (PsrP-BR) 的配体结合区域的指定 NMR 骨架共振揭示了溶液中的刚性单体。

肺炎球菌富含丝氨酸重复蛋白 (PsrP) 显示在肺炎链球菌的表面在人类上呼吸道的定植中具有建议的作用。全长 PsrP 是一种 4000 个残基长的多结构域蛋白，包含一个带正电荷的功能结合区 (BR) 结构域，用于在肺炎球菌粘附和生物膜形成过程中分别与角蛋白和细胞外 DNA 相互作用。先前确定的 BR 域的晶体结构显示一个扁平的压缩桶，包括两个侧面，一侧有一个延伸的 β-折叠，另一侧是另一个被环和β-转角扭曲的β-折叠。晶体学 B 因子表明环区域的相对较高的流动性，这些区域被假设为对结合很重要。此外，晶体结构揭示了在两个对称相关分子的边缘链之间形成的分子间β-折叠，这可以促进生物膜形成过程中的细菌聚集。在这里，我们报告接近完成PsrP 的 BR 结构域的¹⁵ N/ ¹³ C/ ¹ H 骨架共振分配，揭示了与 X 射线结构几乎相同的二级结构剖面。动态¹⁵ N-T ₁、T ₂和NOE数据表明BR的单体和刚性结构仅在N-和C-末端具有无序残基。所呈现的峰值分配将使我们能够识别对配体结合至关重要的 BR 残基。