时间：2022年11月30日（星期三）8:30-10:30

腾讯会议会议号：165-694-139

主办：华中农业大学

承办：动物科学技术学院动物医学院

报告人1：舒盛8:30-9:30

题目：大肠杆菌合成脂多糖的调控机理

Regulatory mechanisms of lipopolysaccharide synthesis in Escherichia coli

摘要：脂多糖(LPS)是一种必需的糖脂，在大多数革兰氏阴性细菌表面形成保护性渗透屏障。在大肠杆菌中，脱乙酰酶LpxC催化LPS合成中的第一个关键步骤，并且决定了细胞中LPS的水平。大肠杆菌中LPS的含量处于反馈控制之下，这是通过FtsH介导的LpxC降解实现的。FtsH是一种膜结合的AAA+蛋白酶，其对LpxC的蛋白酶活性受到两个必需的膜蛋白LapB和YejM调节。然而，人们并不清楚LapB和YejM参与调控FtsH对LpxC进行降解的具体机理。我们建立了一种体外方法来分析LpxC降解的酶促反应动力学，并证明LapB是一种配体蛋白，它利用其跨膜螺旋与AAA+蛋白酶FtsH相互作用，并利用其细胞质结构域募集底物LpxC。我们的YejM/LapB复合结构表明YejM是一种反配体蛋白，与FtsH竞争LapB以抑制LpxC降解。结构分析表明LapB和LPS在YejM中具有重叠的结合位点。因此，LPS水平控制YejM/LapB复合物的形成从而决定了LpxC蛋白水平。

Lipopolysaccharide (LPS) is an essential glycolipid and forms a protective permeability barrier for most Gram-negative bacteria. In E. coli, LPS levels are under feedback control, achieved by FtsH-mediated degradation of LpxC, which catalyzes the first committed step in LPS synthesis. FtsH is a membrane-bound AAA+ protease, and its protease activity toward LpxC is regulated by essential membrane proteins LapB and YejM. However, the regulatory mechanisms are elusive. We establish an in vitro assay to analyze the kinetics of LpxC degradation and demonstrate that LapB is an adaptor protein that utilizes its transmembrane helix to interact with FtsH and its cytoplasmic domains to recruit LpxC. Our YejM/LapB complex structure reveals that YejM is an anti-adaptor protein, competing with FtsH for LapB to inhibit LpxC degradation. Structural analysis unravels that LapB and LPS have overlapping binding sites in YejM. Thus, LPS levels control formation of the YejM/LapB complex to determine LpxC protein levels.

报告人2：叶刚9:30-10:30

题目:利用噬菌体展示技术开发新冠病毒纳米抗体

The development of anti-SARS-CoV-2 nanobody using phage display technology

摘要:抗击新冠肺炎需要高效且低价的治疗药物。中和抗体具有特异性强，安全性高的特点。纳米抗体发现于骆驼科及一些鲨鱼体内，是一种单链抗体，与传统抗体相比拥有很多优点。本研究基于已有的天然纳米抗体噬菌体库，筛选出可以中和新冠病毒的纳米抗体nanosota-1.通过体外引入突变，提高了抗体的效力。RBD与纳米抗体的复合物结构表明纳抗结合在RBM区域，与受体ACE2存在竞争。进一步的动物攻毒实验表明，Nanosota-1C-Fc对SARS-CoV-2感染有良好的预防和治疗效果。同时，Nanosota-1C-Fc可以在细菌中高效表达，在体外和体内均具有高稳定性。因此，Nanosota-1C-Fc是一个潜在的新冠病毒候选药物。

Combating the COVID-19 pandemic requires potent and low-cost therapeutics. Neutralizing antibodies are ideal drugs because of its high specificity and safety. Nanobodies discovered in camelid and shark, are single domain antibodies and have many advantages compared to conventional antibodies. This study identified a SARS-CoV-2 neutralizing nanobody, nanosota-1, from a camelid nanobody phage display library. The efficacy of nanosota-1 was greatly improved by introducing of mutations by in vitro affinity maturation. Structural data showed that Nanosota-1C bound to the RBM of SARS-CoV-2 spike receptor-binding domain (RBD), blocking viral receptor ACE2. In animal study, Nanosota- 1C-Fc demonstrated preventive and therapeutic efficacy against live SARS-CoV-2 infection in both hamster and mouse models. Unlike conventional antibodies, Nanosota-1C-Fc was produced at high yields in bacteria and had exceptional stability both in vitro and in vivo. Thus, Nanosota-1C-Fc is an effective and inexpensive drug candidates of COVID-19。