Single-molecule counting techniques enable a precise determination of the intracellular abundance and stoichiometry of proteins and macromolecular complexes. These details are often challenging to quantitatively assess yet are essential for our understanding of cellular function. Consider G-protein-coupled receptors—an expansive class of transmembrane signaling proteins that participate in many vital physiological functions making them a popular target for drug development. While early evidence for the role of oligomerization in receptor signaling came from ensemble biochemical and biophysical assays, innovations in single-molecule measurements are now driving a paradigm shift in our understanding of its relevance. Here, we review recent developments in single-molecule counting with a focus on photobleaching step counting and the emerging technique of quantitative single-molecule localization microscopy—with a particular emphasis on the potential for these techniques to advance our understanding of the role of oligomerization in G-protein-coupled receptor signaling.

单分子计数技术能够精确测定蛋白质和大分子复合物的细胞内丰度和化学计量。这些细节通常难以定量评估，但对于我们理解细胞功能至关重要。以 G 蛋白偶联受体为例，它是一类广泛的跨膜信号蛋白，参与许多重要的生理功能，使其成为药物开发的热门目标。虽然寡聚化在受体信号传导中作用的早期证据来自整体生化和生物物理测定，但单分子测量的创新现在正在推动我们对其相关性的理解发生范式转变。在这里，我们回顾了单分子计数的最新进展，重点是光漂白步数计数和定量单分子定位显微镜的新兴技术，特别强调这些技术有可能促进我们对寡聚化在细胞中的作用的理解。 G 蛋白偶联受体信号传导。