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首页> 外文期刊>Journal of Molecular Biology >Crystal structure of the peptidoglycan recognition protein at 1.8 A resolution reveals dual strategy to combat infection through two independent functional homodimers.
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Crystal structure of the peptidoglycan recognition protein at 1.8 A resolution reveals dual strategy to combat infection through two independent functional homodimers.

机译：肽聚糖识别蛋白在1.8 A分辨率下的晶体结构揭示了通过两个独立的功能同型二聚体对抗感染的双重策略。

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The mammalian peptidoglycan recognition protein-S (PGRP-S) binds to peptidoglycans (PGNs), which are essential components of the cell wall of bacteria. The protein was isolated from the samples of milk obtained from camels with mastitis and purified to homogeneity and crystallized. The crystals belong to orthorhombic space group I222 with a=87.0 A, b=101.7 A and c=162.3 A having four crystallographically independent molecules in the asymmetric unit. The structure has been determined using X-ray crystallographic data and refined to 1.8 A resolution. Overall, the structures of all the four crystallographically independent molecules are identical. The folding of PGRP-S consists of a central beta-sheet with five beta-strands, four parallel and one antiparallel, and three alpha-helices. This protein fold provides two functional sites. The first of these is the PGN-binding site, located on the groove that opens on the surface in the direction opposite to the location of the N terminus. The second site is implicated to be involved in the binding of non-PGN molecules, it also includes putative N-terminal segment residues (1-31) and helix alpha2 in the extended binding. The structure reveals a novel arrangement of PGRP-S molecules in which two pairs of molecules associate to form two independent dimers. The first dimer is formed by two molecules with N-terminal segments at the interface in which non-PGN binding sites are buried completely, whereas the PGN-binding sites of two participating molecules are fully exposed at the opposite ends of the dimer. In the second dimer, PGN-binding sites are buried at the interface while non-PGN binding sites are fully exposed at the opposite ends of the dimer. This form of dimeric arrangement is unique and seems to be aimed at enhancing the capability of the protein against specific invading bacteria. This mode of functional dimerization enhances efficiency and specificity, and is observed for the first time in the family of PGRP molecules.
机译：哺乳动物肽聚糖识别蛋白-S（PGRP-S）与肽聚糖（PGNs）结合，后者是细菌细胞壁的重要组成部分。从得自患有乳腺炎的骆驼的牛奶样品中分离蛋白质，纯化至均质并结晶。晶体属于正交晶体空间群I222，其a = 87.0 A，b = 101.7 A和c = 162.3 A，在不对称单元中具有四个晶体学独立的分子。使用X射线晶体学数据确定了结构，并将其精炼为1.8 A分辨率。总体而言，所有四个晶体学独立分子的结构都是相同的。 PGRP-S的折叠包括一个中央β-折叠，该折叠带有五个β-链，四个平行和一个反平行以及三个α-螺旋。该蛋白质折叠提供两个功能位点。第一个是PGN结合位点，位于与N端位置相反的方向在表面上开口的凹槽中。第二个位点暗示与非PGN分子的结合有关，它在扩展的结合中还包括推定的N末端片段残基（1-31）和螺旋α2。该结构揭示了PGRP-S分子的新颖排列，其中两对分子缔合形成两个独立的二聚体。第一二聚体由在其非PGN结合位点完全掩埋的界面上具有N末端片段的两个分子形成，而两个参与分子的PGN结合位点在二聚体的相对端完全暴露。在第二个二聚体中，PGN结合位点埋在界面处，而非PGN结合位点则在二聚体的相对末端完全暴露。这种形式的二聚体排列是独特的，似乎旨在增强蛋白质抵抗特定入侵细菌的能力。功能性二聚化的这种模式提高了效率和特异性，并且在PGRP分子家族中首次观察到。

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