Molecular and supramolecular studies on polyglycine and poly-L-proline
Molecular and supramolecular studies on polyglycine and poly-L-proline
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DOI：
10.1039/c1sm05726j
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发表时间：
2011-01-01
期刊：
影响因子：
3.4
通讯作者：
Bochicchio, Brigida
中科院分区：
文献类型：
--
作者：
Lorusso, Marina;Pepe, Antonietta;Bochicchio, Brigida
弹性蛋白是一种交联蛋白，其可溶性前体是弹性蛋白原，负责脊椎动物组织的弹性和弹性回缩。甘氨酸和脯氨酸是弹性蛋白原一级结构中重复次数最多的氨基酸之一，高柔性甘氨酸出现了 222 次，而限制性较大的脯氨酸出现了 96 次。为了更深入地研究甘氨酸和脯氨酸残基在弹性蛋白中的作用，我们研究了聚甘氨酸和聚L-脯氨酸同聚肽的分子和超分子结构作为蛋白质的重要序列。事实上，到目前为止，如果仅对溶液中的聚-L-脯氨酸同聚肽和固态聚甘氨酸同聚肽进行构象研究很少，那么对这两种同聚肽的超分子研究也很有限。鉴于这些同聚肽的自聚集特性，我们通过比浊法测量以及刚果红双折射测定、ThT荧光光谱、原子力显微镜和透射电子显微镜研究研究了聚集机制。在分子水平上，我们显示了聚甘氨酸原纤维的交叉b结构占主导地位，而对于聚-L-脯氨酸聚集体，PPII构象占主导地位。在超分子水平上，结果表明，聚甘氨酸能够自我聚集成淀粉样蛋白纤维，而聚L-脯氨酸则通过遵循从原纤维到原纤维的特定途径聚集。这些发现表明，弹性蛋白的自聚集特性受到原弹性蛋白一级结构的影响，从而解释了为什么富含甘氨酸的弹性蛋白衍生的多肽序列具有淀粉样变性（Gly效应），而富含脯氨酸的弹性蛋白衍生的多肽序列（Pro效应）能够凝聚。
Elastin is a cross-linked protein, whose soluble precursor is tropoelastin, responsible for resilience and elastic recoil in vertebrate tissues. Glycine and proline are among the most repeated amino acids in tropoelastin primary structure, the high flexible glycine being present 222 times and the more constrained proline being present 96 times. In order to deeper investigate the role of glycine and proline residues in elastin, we studied the molecular and supramolecular structures of polyglycine and poly-L-proline homopolypeptides as significant sequences for the protein. As a matter of fact, up to now, if few conformational studies are accessible only for poly-L-proline homopolypeptide in solution and for polyglycine homopolypeptide in the solid state, limited supramolecular studies are available for both homopolypeptides. Given the self-aggregation properties of these homopolypeptides, we investigated the aggregation mechanism by turbidimetry measurements together with Congo red birefringence assay, ThT fluorescence spectroscopy, and atomic force microscopy and transmission electron microscopy studies. At molecular level, we show the dominance of the cross-b structure for polyglycine fibrils while for poly-L-proline aggregates PPII conformation prevails. At supramolecular level, the results show that polyglycine is able to self-aggregate into amyloid-like fibres while poly-L-proline aggregates by following a specific pathway ranging from protofibrils to fibrils. These findings suggest that the self-aggregation properties of elastin are influenced by tropoelastin primary structure thus explaining why glycine-rich elastin-derived polypeptide sequences are amyloidogenic (Gly-effect) while proline-rich elastin-derived polypeptide sequences (Pro-effect) are able to coacervate.