Many discoveries in cell biology rely on making specific proteins visible within their native cellular environment. There are various genetically encoded tags, such as fluorescent proteins, developed for fluorescence microscopy (FM). However, there are almost no genetically encoded tags that enable cellular proteins to be observed by both FM and electron microscopy (EM). Herein, we describe a technology for labeling proteins with diverse chemical reporters, including bright organic fluorophores for FM and electron-dense nanoparticles for EM. Our technology uses versatile interacting peptide (VIP) tags, a class of genetically encoded tag. We present VIPER, which consists of a coiled-coil heterodimer formed between the genetic tag, CoilE, and a probe-labeled peptide, CoilR. Using confocal FM, we demonstrate that VIPER can be used to highlight subcellular structures or to image receptor-mediated iron uptake. Additionally, we used VIPER to image the iron uptake machinery by correlative light and EM (CLEM). VIPER compared favorably with immunolabeling for imaging proteins by CLEM, and is an enabling technology for protein targets that cannot be immunolabeled. VIPER is a versatile peptide tag that can be used to label and track proteins with diverse chemical reporters observable by both FM and EM instrumentation.

细胞生物学中的许多发现都依赖于使特定蛋白质在其天然细胞环境中可见。存在用于荧光显微镜（FM）的各种遗传编码标签，例如荧光蛋白。但是，几乎没有遗传编码的标签可以使FM和电子显微镜（EM）都能观察到细胞蛋白。在本文中，我们描述了一种使用多种化学报道分子标记蛋白质的技术，包括用于FM的明亮有机荧光团和用于EM的电子致密纳米粒子。我们的技术使用多功能相互作用肽（VIP）标签，这是一类经过遗传编码的标签。我们介绍VIPER，它由在遗传标签CoilE和探针标记的肽CoilR之间形成的卷曲螺旋异二聚体组成。使用共聚焦FM 我们证明VIPER可用于突出亚细胞结构或图像受体介导的铁摄取。此外，我们使用VIPER通过相关光和EM（CLEM）对铁的摄取机械进行成像。VIPER与CLEM对蛋白质成像进行免疫标记相比具有优势，并且是一种无法进行免疫标记的蛋白质靶标的启用技术。VIPER是一种多功能肽标签，可用于通过FM和EM仪器观察到的多种化学报告基因标记和跟踪蛋白质。