Protein-protein interactions (PPIs) stand at the heart of most cellular processes and control the vast majority of biological systems, especially in mediating functions such as sensing the environment, mediating signal transduction, and adjusting the activity of metabolic and signaling enzymes. Protein-protein interaction (PPI) has already become one of the major objectives in structural biology and life science. Nowadays, Creative Biolabs contributes various experimental and bioinformatic studies to helping scientists deepen understanding of protein interactions and improve our capacity to predict them.
Fig.1 Timeline of protein-protein interaction research.
Protein-protein interactions are physical contacts of specificity established between two or more protein molecules and caused by electrostatic forces including the hydrophobic effect. Based on their characteristics, PPIs can be classified in several ways. Considering their interaction surface, they may be homo- or heterooligomeric; as measured by stability, they could be obligate or nonobligate; when judged by their persistence, they may be transient or permanent. A given protein’s interaction may be a combination of these three specific pairs.
In brief, PPIs fundamentally could be characterized as stable or transient. Both stable and transient interactions can be either strong or weak, fast or slow. The transient interactions would form signaling pathways while stable ones will produce a stable protein complex. Generally, stable interactions are best detected by co-immunoprecipitation, pull-down or far-Western assays and transient interactions can be captured by crosslinking or label transfer methods.
Fig.2 Different levels of characterization of protein interactions in vivo and in vitro.
In Creative Biolabs, PPI detection approaches are classified into three types, in vivo, in vitro, and in silico methods.
|In vivo||Yeast two-hybrid (Y2H)||Bacterial two-hybrid (B2H) system|
|Bioluminescence resonance energy transfer (BRET)||Fluorescence resonance energy transfer (FRET)|
|Bimolecular fluorescence complementation (BiFC)||Proximity-dependent Biotin Identification (BioID)|
|In vitro||Tandem affinity purification (TAP)||Affinity chromatography|
|Co-immunoprecipitation (Co-IP)||Pull-down assay|
|Protein arrays||Protein-fragment complementation assay (PCA)|
|Phage display||X-ray crystallography|
|Surface plasmon resonance (SPR)||Nuclear magnetic resonance spectroscopy (NMR spectroscopy)|
|In silico||Gene fusion||Sequence-based approaches|
|Chromosome proximity||Structure-based approaches|
|In silico two hybrid||Mirror tree|
|Phylogenetic tree||Gene expression-based approaches|
Table 1. Protein-protein interaction services.
Besides the conventional and widely used approaches to detect protein-protein interaction, we have also developed several novel platforms to meet specific requirements, such as Magic™ Conversable Mammalian Library (CML) Platform for Biomolecular Interaction Discovery.
The result of two or more proteins that interact with each other can be demonstrated in different ways. The measurable biological effects of PPIs have been outlined as follows:
PPIs handle a wide range of biological processes, ranging from cell-to-cell interactions to metabolic and developmental control. At present, PPI is one of the key topics for the development and progress of modern systems biology. Creative Biolabs focuses on all available biochemical methods and advanced biophysical techniques for identifying associated protein molecules and dissecting cellular protein interactors functions under well-defined conditions. Furthermore, usually a combination of techniques is necessary to test, validate and confirm protein interactions in an experimental design of Creative Biolabs. In this respect, data and information obtained from many different perspectives are much more reliable and comprehensive.