Signaling Proteins as Internal Loading Controls

Normalization Webinar InvitationFor more information on Western blot normalization, watch these webinars:


Besides housekeeping proteins and total protein controls, signaling proteins are another option for normalization. This approach is particularly useful for relative analysis of post-translational modifications such as phosphorylation. The method combines two primary antibodies raised in different hosts: a phospho-specific antibody (or other modification-specific antibody) and a pan-specific antibody that recognizes the target protein regardless of its modification state. Fluorescently-labeled secondary antibodies are used to simultaneously detect and discriminate the two signals with digital imaging. Phospho-signal is then normalized against the total level of target protein, using the target protein as its own internal control.

This is a great strategy to use if you’re studying protein modifications. Bakkenist et al. examined the possibility of binding interference from combined phospho-specific and pan antibodies, but detected little or no effect.
signaling-protein
Advantages of Phospho-Analysis with Signaling Proteins:

  • You can detect both unmodified and modified forms of your target protein on the same blot, in the same lane.
  • No error is introduced by stripping and reprobing. Stripping and reprobing of blots can introduce detection artifacts and cause loss of blotted proteins from the membrane.
  • Accuracy is improved by correcting for loading and sampling error

Find out more about multiplex analysis using signaling proteins: Western Blot Normalization: Challenges and Considerations for Quantitative Analysis

Types of Normalization Strategies

Normalization Webinar InvitationFor more information on Western blot normalization, watch these webinars:


Western Story - GlovedScientistsWhat normalization strategies are available to you when performing Western blots? The next four blog posts in this series will discuss the options that exist and considerations for use of each strategy.

An ideal internal loading control would have a linear, proportional response, be stably expressed in all experimental conditions, correct for variation throughout the whole process of immunoblotting, and be compatible with detection of your target proteins.

If you have the time to validate your loading control for each experiment, a housekeeping protein may work for you. You must validate all your housekeeping proteins to ensure stable expression.

If you’re studying protein modifications, like phosphorylation, ubiquitination, or glycosylation, then a multiplex normalization strategy with a signaling protein is recommended.

Total protein controls use all proteins present in the sample, and include total protein stains. If you don’t have time to validate, a total protein stain is best.

There are many ways to normalize. The best way depends on you and your experimental context. Watch for future blog posts about housekeeping proteins, signaling proteins, and total protein stains.

Find out more about normalization: Western Blot Normalization: Challenges and Considerations for Quantitative Analysis