Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States.
Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States.
Elife. 2021 Aug 19;10:e69742. doi: 10.7554/eLife.69742.
NmMetQ is a substrate-binding protein (SBP) from that has been identified as a surface-exposed candidate antigen for meningococcal vaccines. However, this location for NmMetQ challenges the prevailing view that SBPs in Gram-negative bacteria are localized to the periplasmic space to promote interaction with their cognate ABC transporter embedded in the bacterial inner membrane. To elucidate the roles of NmMetQ, we characterized NmMetQ with and without its cognate ABC transporter (NmMetNI). Here, we show that NmMetQ is a lipoprotein (lipo-NmMetQ) that binds multiple methionine analogs and stimulates the ATPase activity of NmMetNI. Using single-particle electron cryo-microscopy, we determined the structures of NmMetNI in the presence and absence of lipo-NmMetQ. Based on our data, we propose that NmMetQ tethers to membranes via a lipid anchor and has dual function and localization, playing a role in NmMetNI-mediated transport at the inner membrane and moonlighting on the bacterial surface.
NmMetQ 是一种来自 的底物结合蛋白 (SBP)，已被鉴定为脑膜炎球菌疫苗的表面暴露候选抗原。然而，NmMetQ 的这种位置挑战了普遍认为的观点，即革兰氏阴性菌中的 SBPs 定位于周质空间，以促进与嵌入细菌内膜的同源 ABC 转运体相互作用。为了阐明 NmMetQ 的作用，我们对带有和不带有其同源 ABC 转运体 (NmMetNI) 的 NmMetQ 进行了表征。在这里，我们表明 NmMetQ 是一种脂蛋白 (lipo-NmMetQ)，可结合多种蛋氨酸类似物并刺激 NmMetNI 的 ATP 酶活性。使用单颗粒电子低温显微镜，我们确定了存在和不存在 lipo-NmMetQ 时的 NmMetNI 结构。基于我们的数据，我们提出 NmMetQ 通过脂质锚定与膜结合，并具有双重功能和定位，在 NmMetNI 介导的内膜转运中发挥作用，并在细菌表面兼职。
