Probing cellular protein complexes using single-molecule pull-down

Ankur Jain, Ruijie Liu, Biswarathan Ramani, Edwin Arauz, Yuji Ishitsuka, Kaushik Ragunathan, Jeehae Park, Jie Chen, Yang K. Xiang, Taekjip Ha

Research output: Contribution to journalArticlepeer-review

264 Scopus citations


Proteins perform most cellular functions in macromolecular complexes. The same protein often participates in different complexes to exhibit diverse functionality. Current ensemble approaches of identifying cellular protein interactions cannot reveal physiological permutations of these interactions. Here we describe a single-molecule pull-down (SiMPull) assay that combines the principles of a conventional pull-down assay with single-molecule fluorescence microscopy and enables direct visualization of individual cellular protein complexes. SiMPull can reveal how many proteins and of which kinds are present in the in vivo complex, as we show using protein kinase A. We then demonstrate a wide applicability to various signalling proteins found in the cytosol, membrane and cellular organelles, and to endogenous protein complexes from animal tissue extracts. The pulled-down proteins are functional and are used, without further processing, for single-molecule biochemical studies. SiMPull should provide a rapid, sensitive and robust platform for analysing protein assemblies in biological pathways.

Original languageEnglish (US)
Pages (from-to)484-488
Number of pages5
Issue number7348
StatePublished - May 26 2011
Externally publishedYes

ASJC Scopus subject areas

  • General


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