School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
Proc Natl Acad Sci U S A. 2011 Feb 22;108(8):3175-80. doi: 10.1073/pnas.1012842108. Epub 2011 Feb 7.
Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO(2) (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano- to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines and phosphoproteins (silaffins and silacidins), which are readily soluble in water, and spontaneously form dynamic supramolecular assemblies that accelerate silica deposition and influence silica morphogenesis in vitro. However, synthesis of diatom-like silica structure in vitro has not yet been accomplished, indicating that additional components are required. Here we describe the discovery and intracellular location of six novel proteins (cingulins) that are integral components of a silica-forming organic matrix (microrings) in the diatom Thalassiosira pseudonana. The cingulin-containing microrings are specifically associated with girdle bands, which constitute a substantial part of diatom biosilica. Remarkably, the microrings exhibit protein-based nanopatterns that closely resemble characteristic features of the girdle band silica nanopatterns. Upon the addition of silicic acid the microrings become rapidly mineralized in vitro generating nanopatterned silica replicas of the microring structures. A silica-forming organic matrix with characteristic nanopatterns was also discovered in the diatom Coscinodiscus wailesii, which suggests that preassembled protein-based templates might be general components of the cellular machinery for silica morphogenesis in diatoms. These data provide fundamentally new insight into the molecular mechanisms of biological silica morphogenesis, and may lead to the development of self-assembled 3D mineral forming protein scaffolds with designed nanopatterns for a host of applications in nanotechnology.
硅藻是产生由二氧化硅（SiO2）制成的具有物种特异性结构细胞壁的真核微藻。硅藻复杂的硅质结构的形成被认为是生物分子控制三维、纳米到微尺度图案化无机材料自组装的典范。硅的形成涉及长链多胺和磷蛋白（硅甲素和硅丙氨酸），它们在水中易溶，并自发形成动态超分子组装体，加速硅的沉积并影响体外的硅形态发生。然而，体外还没有完成类似硅藻的硅结构的合成，这表明还需要其他成分。在这里，我们描述了在硅藻塔玛斯伪诺纳中发现的六种新蛋白质（cingulins）的发现和细胞内位置，它们是形成硅的有机基质（microrings）的组成部分。含 cingulin 的 microrings 与腰带带紧密相关，腰带带构成硅藻生物硅的重要部分。值得注意的是，microrings 表现出与腰带带硅纳米图案特征密切相似的基于蛋白质的纳米图案。在添加硅酸后，microrings 在体外迅速矿化，生成 microring 结构的纳米图案化硅复制品。在硅藻 Coscinodiscus wailesii 中也发现了具有特征纳米图案的硅形成有机基质，这表明预先组装的基于蛋白质的模板可能是硅藻中硅形态发生的细胞机制的一般组成部分。这些数据为生物硅形态发生的分子机制提供了全新的见解，并可能导致具有设计纳米图案的自组装 3D 矿物形成蛋白支架的开发，用于纳米技术中的各种应用。
