The Protein Interactions Expert

ULTImate Y2H: our Yeast two-hybrid screening service

9000 screens performed

The most comprehensive yeast two-hybrid screening technology. 

ULTImate Y2H™ is an optimized version of the yeast two-hybrid (Y2H) screening technique to discover novel protein interactions. Unlike classical Y2H sequential transformation protocols, ULTImate Y2H™ takes advantage of our patented cell-to-cell mating process to test on average 83 million interactions per screen.

This guarantees that our highly complex domain libraries are screened to saturation for every project. As a consequence, even rare partners or transient interactions can be detected, with a high reproducibility. This enables the accurate comparison of protein interaction maps obtained from wild-type proteins or mutants.

Conversely, our unmatched experience and unique bioinformatics capabilities allow us to flag the technical false positives and compute a confidence score for each interaction.

CONTACT US now for a detailed explanation and visit our resource center.


  • Discover novel protein partners for your favorite protein
  • Elucidate mechanisms of action
  • Ascribe functions to uncharacterized proteins
  • Unravel pathways and molecular machines

Molecules tested

  • Full-length proteins or fragments, peptides
  • Cytoplasmic or extracellular proteins
  • Loops and tails of membrane proteins

Highly complex domain libraries screened to saturation

  • Choose from the largest collection of cDNA or genomic libraries, or request a custom library
  • Benefit from the most complex random-primed cDNA libraries, with 10 million primary clones in yeast
  • All libraries are screened to saturation by covering 10 times their complexity on average

yeast two-hybrid principle diagram

How does it work?

ULTImate Y2H™ is based on the reconstitution of a functional transcription factor (TF) followed by the expression of a reporter gene in genetically modified yeast cells. Upon physical binding of your protein of interest (bait) to a protein fragment from the library (prey), the DNA Binding Domain (DBD) of the TF is brought in close proximity to its Activation Domain (AD). Reconstitution of the functional TF activates the transcription of the HIS3 reporter gene, which allows yeast cells to grow on a selective medium lacking histidine. The DNA of the positive clones is then sequenced and analyzed to identify the protein partners.

We also offer ULTImate Y2H+1, a modified version of our ULTImate Y2H process that allows the stable expression in yeast of any co-factor required for the proper folding or posttranslational modification of the bait (tyrosine kinase...)

More information on the Y2H in general and a comparison with other protein interaction techniques can be found in the resource section.

Yeast Two-Hybrid mating procedure: ULTImate

Key Benefits

  • Fast and exhaustive screening of highly complex libraries thanks to Hybrigenics patented cell-to-cell mating protocol
  • Detection of even weak interactions and interactions from the rarest transcripts
  • Up to 380 positive clones analyzed (5’ and 3’ sequences)
  • Sophisticated bioinformatics analysis of the results including confidence scores
  • An additional screening included if the initial results provide less than 20 positive clones
  • Scientific and technical assistance for the best outcome of your project, from bait design to the review of your results in person or over the phone.


The results of your ULTImate Y2H screen come fully analyzed to help you focus on the most relevant interactions. The deliverables include the list of identified protein partners, the experimental interaction domain on each protein and a confidence score. Please click here for a detailed presentation.

Application Examples

More than 500 publications by our customers are based on ULTImate Y2H results! Please browse the list here.

Please see examples of successful ULTImate Y2H+1 screens: Naba et al., 2008 and Zaarour et al., 2012.

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