胞壁肽连接酶（MpI）为肽聚糖循环过程中的关键酶之一，其分子调控机制不清楚。我们在CRISPR/Cas9技术构建的ftsZ敲除大肠埃希菌中发现其肽聚糖循环增强和耐药性降低，且伴随MpI表达上调。本课题研究FtsZ通过何种分子机制调控MpI表达并影响肽聚糖循环和耐药性。拟在ftsZ敲除细菌中抑制MpI酶，检测其肽聚糖循环和耐药性是否得到纠正，明确FtsZ是通过MpI这个环节来影肽聚糖循环和耐药性。我们前期实验表明，FtsZ并不是以转录调控方式影响MpI表达；生物信息学分析FtsZ和MpI存在潜在相互作用，提示FtsZ可能以翻译后蛋白修饰方式调控mpI的表达。我们将用免疫共沉淀（Co-Immunoprecipitation，Co-IP)、质谱分析以及pull-down等技术首先验证FtsZ和MpI之间是否真实存在直接相互作用；其次分析和FtsZ可能作用的其他蛋白。通过AAA+蛋白酶、原核生物类泛素蛋白酶体等降解调控实验，探明FtsZ对MpI修饰方式。

Murein peptide ligase (MpI) is one of pivotal enzymes in the process of peptidoglycan recycling while the mechanism of molecular regulation remains unclear. We unexpectedly detected high repetition rate of peptidoglycan and Low resistance along with a significant up-regulation of MpI in the ftsZ-deficient escherichia coli generated by the clustered regularly interspersed short palindromic repeats cas9（CRISPR/Cas9）strategy. Thus, the goal of this study is to clarify the molecular mechanism of FtsZ influence peptidoglycan recycling via MpI. First of All, to determine whether MpI mainly mediates peptidoglycan recycling caused by FtsZ difficiency, we are going to inhibit MpI in the ftsZ-deficient escherichia coli for rescuing the peptidoglycan recycling and resistance. In the ftsZ-deficient escherichia coli, our previous data showed that there was not significant change in the mRNA level of mpI compared with the wild escherichia coli, suggesting that FtsZ doesn’t influence the transcription regulation of mpI. According to the bioinformatics analysis of FtsZ which potentially directly interact with MpI, we assume that FtsZ would like to take effort on the expression level of MpI by degradation way. In this study, we plan to apply mass spectrometry, Co-Immunoprecipitation (Co-IP) with pull-down to confirm the direct interaction between FtsZ and MpI, meanwhile predict to other potential proteins may interact with FtsZ. Ultimately, we want to illuminate the specifically posttranslational modification of FtsZ towards MpI thoroughly by the experiments of ATPases associated with diverse cellular activities proteasome (AAA+ proteasome) and like ubiquitin-proteasome.