Mezzina Mariela P, Pettinari M Julia
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, Buenos Aires, Argentina.
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, Buenos Aires, Argentina
Appl Environ Microbiol. 2016 Aug 15;82(17):5060-7. doi: 10.1128/AEM.01161-16. Print 2016 Sep 1.
Phasins are the major polyhydroxyalkanoate (PHA) granule-associated proteins. They promote bacterial growth and PHA synthesis and affect the number, size, and distribution of the granules. These proteins can be classified in 4 families with distinctive characteristics. Low-resolution structural studies and in silico predictions were performed in order to elucidate the structure of different phasins. Most of these proteins share some common structural features, such as a preponderant α-helix composition, the presence of disordered regions that provide flexibility to the protein, and coiled-coil interacting regions that form oligomerization domains. Due to their amphiphilic nature, these proteins play an important structural function, forming an interphase between the hydrophobic content of PHA granules and the hydrophilic cytoplasm content. Phasins have been observed to affect both PHA accumulation and utilization. Apart from their role as granule structural proteins, phasins have a remarkable variety of additional functions. Different phasins have been determined to (i) activate PHA depolymerization, (ii) increase the expression and activity of PHA synthases, (iii) participate in PHA granule segregation, and (iv) have both in vivo and in vitro chaperone activities. These properties suggest that phasins might play an active role in PHA-related stress protection and fitness enhancement. Due to their granule binding capacity and structural flexibility, several biotechnological applications have been developed using different phasins, increasing the interest in the study of these remarkable proteins.
聚羟基脂肪酸酯结合蛋白是主要的与聚羟基脂肪酸酯（PHA）颗粒相关的蛋白质。它们促进细菌生长和PHA合成，并影响颗粒的数量、大小和分布。这些蛋白质可分为4个具有不同特征的家族。为了阐明不同聚羟基脂肪酸酯结合蛋白的结构，进行了低分辨率结构研究和计算机模拟预测。这些蛋白质大多具有一些共同的结构特征，如主要由α螺旋组成、存在为蛋白质提供灵活性的无序区域以及形成寡聚化结构域的卷曲螺旋相互作用区域。由于其两亲性，这些蛋白质发挥着重要的结构功能，在PHA颗粒的疏水成分和亲水细胞质成分之间形成一个界面。已观察到聚羟基脂肪酸酯结合蛋白会影响PHA的积累和利用。除了作为颗粒结构蛋白的作用外，聚羟基脂肪酸酯结合蛋白还有多种其他功能。已确定不同的聚羟基脂肪酸酯结合蛋白能够：（i）激活PHA解聚，（ii）增加PHA合酶的表达和活性，（iii）参与PHA颗粒的分离，以及（iv）具有体内和体外伴侣活性。这些特性表明聚羟基脂肪酸酯结合蛋白可能在与PHA相关的应激保护和适应性增强中发挥积极作用。由于它们的颗粒结合能力和结构灵活性，已经利用不同的聚羟基脂肪酸酯结合蛋白开发了多种生物技术应用，这增加了人们对研究这些非凡蛋白质的兴趣。
