Function of PhaX in PHB and polyphosphate metabolism in Ralstonia eutropha

真养罗尔斯通氏菌是一种聚（3-羟基丁酸酯）（PHB）和聚磷酸盐（PP）积累化能自养β-变形菌。A_2274产物（具有相邻pitA基因[磷酸盐转运蛋白]的推定磷酸盐转运调节剂）在3个独立的双杂交筛选试验中被鉴定为与PHB颗粒相关蛋白相互作用，即与相蛋白PhaP 2、PhaP 3和与PHB解聚酶PhaZa 1相互作用。相蛋白是存在于所有聚羟基丁酸积累细菌中的小的两亲性蛋白。A_2274与聚羟基丁酸颗粒协会的独立证据，获得了分离的聚羟基丁酸颗粒的蛋白质组分析。A_2274的缺失导致PP的形成增加3倍，并导致PHB的再利用（“动员”）受损。A_2274蛋白存在于分离的PHB颗粒中，其与3种PHB颗粒相关蛋白的体内相互作用以及缺失突变体的表型表明存在PHB代谢和PP之间的联系，因此，A_2274被命名为phaX。本研究的目的是确定PhaX在磷酸盐和PHB代谢中的功能，并了解PHB和PP代谢之间联系的性质。为此，将研究缺失突变体（phaX、pitA、ppk 1、ppk 2、ppx、phoB、phaZa 1、phaC +选定组合）对PP和PHB代谢（包括蛋白质组分析）特定特征的影响。

Ralstonia eutropha is a poly(3-hydroxybutyrate) (PHB) and polyphosphate (PP) accumulating chemolithoautotrophic beta-proteobacterium. The A_2274 product (putative phosphate transport regulator with adjacent pitA gene [phosphate transporter]) was identified in 3 independent 2-hybrid screening assays to interact with PHB granule associated proteins, namely with phasins PhaP2, PhaP3 and with PHB depolymerase PhaZa1. Phasins are small amphiphilic proteins present in all PHB-accumulating bacteria. Independent evidence for the association of A_2274 with PHB granules was obtained by proteome analysis of isolated PHB granules. Deletion of A_2274 resulted in 3-fold increased formation of PP and in impaired reutilization ("mobilization") of PHB. The finding that A_2274 protein is present in isolated PHB granules, its in vivo interaction with 3 PHB granule associated proteins and the phenotype of the deletion mutant suggest the presence of a link between metabolism of PHB and PP; therefore, A_2274 was designated as phaX. The aim of this study is to identify the function of PhaX in phosphate and PHB metabolism and to understand the nature of the link between PHB and PP metabolism. For this, the effect of deletion mutants (phaX, pitA, ppk1, ppk2, ppx, phoB, phaZa1, phaC + selected combinations) on specific features of PP and PHB metabolism including proteome analysis will be investigated.