interacting Protocols

Category: Chromatography Protocols: Affinity Chromatography Protocols

Recombinant protein or a chemically synthesized bioactive fragment is immobilized on resin and used as a probe to capture interacting proteins directly from a cell extract.  Affinity-purified proteins are fractionated by gel electrophoresis and visualized by Coomassie staining.  Proteins that interact specifically are identified by comparing this gel profile to one obtained from cell lysates passed over a control resin lacking the immobilized probe protein. - [Read Affinity Purification of Interacting Proteins from Cell Lysates Protocol]

Category: Immunology: Immunoprecipitation Protocols: Immunoprecipitation of Radiolabeled Cells Protocols

Coimmunoprecipitation is most commonly used to test whether two proteins of interest are associated in vivo, but it can also be used to identify novel interacting partners of a target protein. In both cases, the cells, which may have been labeled with [35S]methionine, are harvested and lysed under conditions that preserve protein-protein interactions. The target protein is specifically immunoprecipitated from the cell extracts, and the immunoprecipitates are fractionated by SDS-PAGE. - [Read Identification of Associated Proteins by Coimmunoprecipitation Protocol]

Category: Immunology: Immunoprecipitation Protocols

Protocol for immunoprecipitation of mRNA-protein complexes. In this protocol, an antibody targeting an RBP of interest is used to immunoprecipitate the RBP and any interacting molecules from a cell lysate. Reverse transcription followed by PCR is then used to identify individual mRNAs isolated with the RBP. This method focuses on examining an association between a specific RBP-mRNA complex, and it is best suited for a small scale screening of known or putative binding partners. - [Read Immunoprecipitation of mRNA-Protein Complexes Protocol]

Category: Primary Cell Isolation and Culture Protocols: Laser Capture Microdissection Protocols

Human tissues are comprised of multiple interacting cell populations in a complex three dimensional arrangement with each cellular phenotype determined by a unique profile of mRNA and protein expression. Before microdissection techniques were developed, the only analysis tools for phenotypic studies were primarily immunohistochemistry and in-situ hybridization. While useful, these tools are limited to single gene analysis and, in general, do not allow qualitative studies. - [Read Microdissection Overview]

Category: Chromatography Protocols: Affinity Chromatography Protocols

Protein complexes can be isolated by several different approaches.  For example, a protein can be tagged with an epitope such as Flag or TAP and then overexpressed in a target cell, allowing the interacting proteins to be purified.  Similarly, epitope tags can be homologously recombined into the endogenous locus ("knocked-in"), allowing protein complexes containing the tagged proteins to be isolated at their natural expression level. - [Read Overview of Affinity Purification in Combination with Mass Spectrometry Protocol]

Category: Reporter Gene Assays: Luciferase Assay Protocols

Protocol describes a split luciferase complementation assay used to study the interaction of proteins in cells. In the split protein strategy, a single reporter protein/enzyme (firefly luciferase [Fluc]) is cleaved into amino-terminal and carboxy-terminal halves; each half is fused to one of two interacting proteins, X & Y. Physical interactions between the two proteins reconstitute the functional reporter protein, leading to enzymatic activities that can be measured by in vitro or in vivo assay - [Read Split Luciferase Complementation Assay for Studying Interaction of Proteins X and Y in Cells]

Category: Immunology: Immunoprecipitation Protocols: Protein Immunoprecipitation Protocols

Protocol describes the use of FLAG-epitope-tagged proteins for both small-scale analysis and large-scale coimmunoprecipitation of interacting proteins. When examining protein interactions, it is sometimes possible to immunoprecipitate an endogenous protein X directly, without using an epitope tag, if antibodies are available. The advantage of examining interactions of endogenously expressed proteins is that these are likely to be physiological and less likely to be an artifact of overexpression. - [Read Using FLAG Epitope-Tagged Proteins for Coimmunoprecipitation of Interacting Proteins Protocol]