Halogenated veneers:: Protein cross-linking and halogenation in the jaws of Nereis, a marine polychaete worm
Halogenated veneers:: Protein cross-linking and halogenation in the jaws of Nereis, a marine polychaete worm
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DOI：
10.1002/cbic.200600160
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发表时间：
2006-09-01
期刊：
影响因子：
3.2
通讯作者：
Waite, J. Herbert
中科院分区：
文献类型：
--
作者：
Birkedal, Henrik;Khan, Rashda K.;Waite, J. Herbert
矿化组织是由大多数生物体产生的负荷和冲击功能。相比之下，蛤虫的下颚在没有矿化的情况下是坚硬的。然而，它们特别富含卤素，这些卤素与各种翻译后修饰的氨基酸有关，其中许多是由氯、溴和/或碘多次卤化的。这些修饰氨基酸中的一些，即二溴组氨酸、溴碘组氨酸、氯碘酪氨酸、溴碘酪氨酸、氯三酪氨酸、氯三酪氨酸、氯三酪氨酸和溴碘三酪氨酸，以前没有报道过。我们发现Cl、Br和I的分布不同：Cl分布广泛，而Br和I虽然没有共定位，但却集中在靠近下颌外表面的地方。通过使用非压痕，我们发现Br和I不太可能发挥纯粹的机械作用，但局部Zn和Cl浓度和颌骨微观结构是局部颌骨硬度的主要决定因素。一些翻译后修饰的氨基酸类似于在无脊椎动物的各种硬化结构中发现的氨基酸，我们提出它们是交联蛋白外壳的一部分。
Mineralized tissues are produced by most living organisms for load and impact functions. In contrast, the jaws of the clam worm, Nereis, are hard without mineralization. However, they are peculiarly rich in halogens, which are associated with a variety of post-translationally modified amino acids, many of which are multiply halogenated by chlorine, bromine, and/or iodine. Several of these modified amino acids, namely dibromohistidine, bromoiodohistidine, chloroiodotyrosine, bromoiodotyrosine, chlorodityrosine, chlorotrityrosine, chlorobromotrityrosine, and bromoiodotrityrosine, have not been previously reported. We have found that the distributions of Cl, Br, and I differ: Cl is widespread whereas Br and I, although not colocalized, are concentrated in proximity to the external jaw surfaces. By using nonoindentation, we show that Br and I are unlikely to play a purely mechanical role, but that the local Zn and Cl concentrations and jaw microstructure are the prime determinants of local jaw hardness. Several of the post-translationally modified amino acids are akin to those found in various sclerotized structures of invertebrates, and we propose that they are part of a cross-linked protein casing.