Illumination of the Structure and Function of PptA, a Novel Type of Polyphosphate Granule Attached Protein in Organelle-like Polyphosphatosomes of Ralstonia eutropha H16

本项目将研究红曲霉PptA蛋白的结构和功能。真养型，其特征在于在P-和N-代谢的边缘处普遍存在（在所有生命界中）CHAD（保守的组氨酸α-螺旋）结构域。PptA具有两个显著的特性：（i）其CHAD结构域以物种独立的方式赋予聚P颗粒特异性结合;（ii）其与N-代谢的关键酶谷氨酰胺合成酶GlnA1相互作用。在这里，我们将确定是否保守序列基序（PptA的等电点为11.5!）或在CHAD蛋白中保守的PptA的其他残基负责与聚阴离子polyP和/或GlnA1相互作用（IEP 5.4）。PptA-GlnA1、PptA-polyP和GlnA1-polyP相互作用的强度和化学计量将通过等温比色滴定（ITC）和/或表面等离子体共振（SPR）来确定。将通过光散射技术测定PptA-GlnA1相互作用对寡聚体状态和活性的影响以及在不同效应分子存在下GlnA1的影响。

In this project we will determine the structure and function of PptA, a protein of R. eutropha that is characterized by an ubiquitously occurring (in all kingdoms of life) CHAD (conserved histidine alpha-helical) domain at the edge of P- and N-metabolism. PptA has two remarkable proterties: (i) it´s CHAD domain confers a specific binding to polyP granules in a species independent manor and (ii) it interacts with the key enzyme of N-metabolism, glutamine synthetase GlnA1. Here, we will determine whether arginines of conserved sequence motifs (isoelectric point of PptA is 11.5!) or other residues of PptA, that are conserved in CHAD proteins, are responsible for interaction with the polyanion polyP and/or GlnA1 (IEP 5.4). The strength and stoichiometry of the PptA-GlnA1, PptA-polyP and GlnA1-polyP interaction will be determined by isothermic colometric titration (ITC) and/or surface plasmon resonance (SPR). The influence of the PptA-GlnA1 interaction on the oligomeric state and activity and of GlnA1 in the presence of different effector molecules will be determined by light scattering technique.