Biomolecular Studies of Biomineralization Proteins: Triplet Motifs

约翰·斯宾塞·埃文斯MCB 98-167031。技术上，矿化结构的生物制造，或生物矿化，是一个生物指导的过程，导致复合材料的形成。与生物矿物相关的一类有趣的蛋白质是所谓的“酸性”蛋白质，它与磷灰石和碳酸钙有关。这些蛋白质含有大量的天冬氨酸、谷氨酸，在某些情况下还含有磷酸化的丝氨酸残基，可以结合Ca(II)离子并启动晶体生长。矛盾的是，这些相同的蛋白质也可能立体地特异性地结合到形成矿物晶体的暴露表面，从而抑制沿着特定结晶轴的生长。但是所有的“酸性”蛋白都是一样的吗？最近的实验表明，所产生的矿物形态与特定蛋白质中的特定氨基酸序列直接相关。最令人兴奋的是，这些蛋白质中的序列重复序列可能代表了一个不同的Ca(II)识别位点和折叠微域的“库”：通过使用相似或不同的序列重复序列组合，给定的“酸性”蛋白质可以“定制”其局部结构以匹配特定的晶体形态或创建特定的晶体形态。这项研究将研究已知的“酸性”序列重复文库中的相似性和差异性。通过使用多学科方法，特定的序列重复将被检查关于Ca(II)的结合、构象变化、晶体生长诱导和晶体形态匹配。这些结果将提供数据库，不仅将促进我们对“酸性”蛋白质结构和功能的理解，还将为合成“模拟多肽”和聚合物的创造提供基础，这些聚合物可以产生新的或重要的晶体形态，并最终产生新的复合材料。作为该项目的一部分，将实施一项涉及高中、大学本科生和研究生的教育战略；将强调独立性、解决问题的能力和团队合作。非技术性有许多自然产生的基于生物的材料，如海贝壳和浮游生物外骨骼，它们是由有机体建造的，用于保护和支持。这些基于生物的材料是独特的，因为它们将无机固体(矿物质)与聚合物(蛋白质、多糖)结合在一起。产生的材料通常非常坚固，并且是由生物在生物条件下组装而成的。因此，“仿生”材料提供了一种新的策略--即使用自组装和分子-分子识别作为“构建技术”--为航空航天、工业和医学创造独特的材料。为了成功地做到这一点，重要的是要了解蛋白质和多糖是如何识别并结合到无机固体上的。这项研究将探索“酸性”蛋白质，如那些在海贝、骨骼和牙齿中发现的蛋白质，如何参与无机-有机复合材料的组装。物理技术的结合将被用来研究在“酸性”蛋白质中发现的序列重复的结构。从这些研究中获得的结果将被用来创建“酸性”蛋白质的分子“蓝图”，其中重要和不重要的矿物识别区域可以被识别出来。最终，这些信息将被用来创造在生物启发的材料组装过程中能够执行特定功能的“设计”蛋白质或聚合物。该研究项目还将作为高中、本科和研究生科学专业培训的教学工具，其中将以解决问题的技能和跨学科培训为特色。

John Spencer EvansMCB 98-167031. TechnicalThe biofabrication of mineralized structures, or biomineralization, is anorganism-directed process which leads to composite material formation. Aninteresting class of biomineral-related proteins are the so-called "acidic"proteins found in association with apatites and calcium carbonates. Theseproteins, which contain significant amounts of Asp, Glu, and in some casesphosphorylated Ser residues, can bind Ca (II) ions and initiate crystalgrowth. Paradoxically, these same proteins may also bind stereospecificallyto the exposed surfaces of forming mineral crystals, thereby inhibitinggrowth along specific crystallographic axes. But are all "acidic" proteinscreated equal? Recent experiments have demonstrated that the resultingmineral morphology is directly related to specific amino acid sequences inspecific proteins. What is most exciting is the possibility that sequencerepeats in these proteins could represent a diverse "library" of Ca (II)recognition sites and folding mini-domains: by using similar or differentcombinations of sequence repeats, a given "acidic" protein could "tailor"its local structure to match a specific crystal morphology or create aspecific crystal morphology. This study will investigate the similaritiesand differences within the known "acidic" sequence repeat library. By usinga multidisciplinary approach, specific sequence repeats will be examinedwith regard to Ca (II) binding, conformational change, crystal growthinduction, and crystal morphology matching. These results will provide adatabase that will not only advance our understanding of "acidic" proteinstructure and function, but also provide the basis for the creation ofsynthetic "peptidomimetics" and polymers that can generate novel orimportant crystal morphologies, and, ultimately, novel composite materials.As part of this project, an educational strategy involving participationof high school, college undergraduate, and graduate students will beimplemented; independence, problem-solving skills and team cooperation willbe emphasized.2. Non-technicalThere are a number of naturally-occurring biological-based materials --such as sea shell and plankton exoskeleton -- which are constructed byorganisms for protection and support. These bio-based materials are unique,in that they combine inorganic solids (minerals) with polymers (proteins,polysaccharides). The resulting materials are usually very strong, and, areassembled by organisms under biological conditions. Hence, "bio-inspired"materials offer a new strategy-- namely, using self-assembly and molecule -molecule recognition as "building techniques" -- for creating uniquematerials for aerospace, industry, and medicine. To do this successfully,it is important to understand how proteins and polysaccharides recognizeand bind to inorganic solids. This research will explore the issue of how"acidic" proteins, such as those found in sea shells, bones, and teeth,participate in the assembly of composite inorganic - organic materials. Acombination of physical techniques will be employed to study the structureof sequence repeats found in "acidic" proteins. The results obtained fromthese studies will be used to create a molecular "blueprint" for "acidic"proteins, wherein important and unimportant regions for mineral recognitioncan be identified. Eventually, this information will be used to create"designer" proteins or polymers which can perform specific functions duringbio-inspired material assembly. This research project will also serve as ateaching tool for the training of high school, undergraduate, and graduatescience majors, wherein problem-solving skills and cross-disciplinetraining will be featured.