How to know the oligomeric state of a protein?

Published Date:
September 4, 2023
Maja Wasilczyk & Courtney Herms
Quality Control

Many proteins are composed of multiple subunits and thus oligomerization is rather the norm than the exception. The association between these subunits can vary in strength and duration.

Protein oligomerisation is a key parameter for a number of reasons, including functional control, such as allosteric regulation, stability and the establishment of higher-order complexity. Thus, understanding the conditions under which protein oligomers form is paramount in drug development, formulation, and bioprocessing. In some cases, oligomerization dependents on environmental conditions, such as concentration, temperature, and pH; other proteins oligomerize dynamically in response to a stimulus, such as a change in protein or nucleotide binding, hydrolysis or post-translational modifications such as phosphorylation and glycosylation.

How to study oligomerization of protein?

Protein oligomers are highly complex molecular structures. Oligomers form by the association of multiple protein subunits, which interact and bind together to create a functional protein assembly. Oligomers can consist of two or more identical or diverse protein subunits. Such complex structures require absolute, quantitative research and analysis methods. Oligomers are essential for many biological processes, including enzyme activity, signal transduction, and structural support within cells.

For studying protein oligomerization, we recommend a quick and quantitative method, which has a high level of pH, concentration and temperature flexibility. Namely, we recommend using a Flow Induced Dispersion Analysis. What does it consist on? FIDA is based on direct, in-solution detection of the size of proteins (hydrodynamic radius). You can read more about how this measurement is taken here. It deliver quantitative data confirming the oligomeric state of the proteins you are analyzing. For your convenience, FIDA allows you to check for oligomerisation as part of your overall functional characterisation, quantification etc. of oligomeric proteins. This can save you both time and sample material.

Remember the impact of the temperature

It is necessary to consider how temperature changes might impact the oligomerisation of your protein of interest. To do this, you need control over the temperature throughout your experiment. The Fida 1 allows you to control the temperature from 5 degrees to 44 degrees with a tolerance of 0.1° C. Thereby it makes it easy to study how temperature changes might impact the oligomerisation.

Oligomeric proteins

Wide range of conditions

Flexible methods make research easier. On top of temperature control, FIDA allows the users to study how different concentrations, pH, ionic strengths, buffers or sample matrices affect the oligomeric state of their protein. Are you interested to see it in practice? See this application note.

FIG 1:TNFa-alexa488 (trimer 3.2 nm) binding to adalimumab with nM affinity in phosphate buffer, 0.067 M, pH 7.4 with 0.1 % HAS, Kd = 1.5 nM, complex size: 8.9 nm

FIG 2: TNFa-alexa488 (trimer 3.2 nm) binding to adalimumab in 10 and 20 % v/v human plasma in phosphate buffer, 0.067 M, pH 7.4 with 0.1 % HAS, Kd = 1.0 – 1.7 nM, complex size: 8.7-9.7 nm
FIG 3: The figure shows the change in hydrodynamic radius (nm) as a function of buffer pH and therefore, the concentration of hydrogen ions (H+). The change in hydrodynamic radius indicates a pH dependent transition of a monomeric state of the protein to an oligomer. Single measurements were performed. R2 = 0.993, Rh, monomer = 1.08 nm, Rh, oligomer = 3.19 nm.

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