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Avidin vs. Streptavidin: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 27, 2024
Avidin is a protein from egg whites that binds strongly to biotin, while streptavidin is a similar biotin-binding protein from the bacterium Streptomyces avidinii.

Key Differences

Avidin, a glycoprotein found in egg whites, is known for its strong and specific binding to the vitamin biotin. Streptavidin, derived from the bacterium Streptomyces avidinii, shares this biotin-binding feature but differs in its source and molecular composition.
Avidin's biotin-binding capability is used in biochemical applications such as purification and detection of biomolecules. Similarly, streptavidin is utilized in these applications, offering the advantage of having no carbohydrate side chains, reducing non-specific binding.
The binding of avidin to biotin is one of the strongest non-covalent interactions in nature. Streptavidin also binds to biotin with high affinity, but its slightly different structure can affect its interaction in some biochemical applications.
Avidin's natural function is to inhibit bacterial growth by sequestering biotin. On the other hand, streptavidin's biological role in its bacterial host is less clear but is thought to involve a similar mechanism of biotin sequestration.
In terms of use in laboratory settings, avidin may cause some issues due to its glycosylation, which can lead to nonspecific binding. Streptavidin is often preferred in certain assays due to its non-glycosylated nature and lower background noise in experiments.

Comparison Chart


Egg whites.
Bacterium Streptomyces avidinii.


Glycosylated protein.
Non-glycosylated protein.

Biotin Binding Affinity

Extremely high.
Extremely high, slightly different interaction.

Biological Role

Biotin sequestration to inhibit bacterial growth.
Less clear, possibly similar biotin sequestration.

Use in Biochemistry

Used in biomolecule purification and detection, with some non-specific binding due to glycosylation.
Preferred for lower non-specific binding, used in similar applications.

Avidin and Streptavidin Definitions


It is a naturally occurring glycoprotein.
The glycosylation of avidin affects its use in certain biochemical assays.


Streptavidin is a protein from Streptomyces avidinii that binds biotin.
Streptavidin was used for its strong biotin-binding ability in the assay.


It plays a role in inhibiting bacterial growth.
The presence of avidin in egg whites helps protect the embryo from bacteria.


Its role in the bacterial host is not as clear as avidin's in egg whites.
Research is ongoing to understand streptavidin's biological role in its bacterial host.


Avidin can cause nonspecific binding in some experiments due to its sugar chains.
Adjustments were made to account for avidin's nonspecific binding in the assay.


Preferred in some biochemical assays for lower background noise.
Streptavidin was chosen over avidin to reduce background in the fluorescence assay.


Avidin is a protein in egg whites binding biotin strongly.
Avidin was used to purify biotin-tagged proteins in the experiment.


It is a non-glycosylated biotin-binding protein.
Streptavidin's lack of glycosylation minimizes nonspecific interactions.


Avidin's strong biotin affinity is leveraged in various laboratory applications.
Avidin-biotin interactions are critical in the immunoassays being developed.


Streptavidin is utilized in biochemistry for its high affinity to biotin.
Streptavidin-biotin complexes are essential in our molecular detection protocols.


A protein found in uncooked egg white that binds to and inactivates biotin.


(protein) A tetrameric protein purified from Streptomyces avidinii that binds very tightly to the vitamin biotin


(biology) A tetrameric protein produced in the oviducts of birds, reptiles and amphibians and deposited in the whites of their eggs.


What is streptavidin?

A biotin-binding protein from Streptomyces avidinii.

What makes streptavidin different from avidin?

It’s non-glycosylated and has slightly different biotin-binding properties.

What is avidin?

A protein in egg whites that binds biotin.

Where is avidin found naturally?

In egg whites.

What's the biotin-binding strength of avidin?

Extremely high, one of the strongest non-covalent interactions.

Is streptavidin always better than avidin?

It depends on the specific requirements of the assay.

What's the source of streptavidin?

The bacterium Streptomyces avidinii.

Why is avidin important in biochemistry?

For its strong biotin-binding capability.

Are there any variants of avidin?

Yes, like NeutrAvidin, with reduced nonspecific binding.

What's a common use of streptavidin in labs?

In affinity chromatography and molecular labeling.

What's a limitation of using avidin?

Its glycosylation can cause non-specific binding.

Can avidin be used in purification processes?

Yes, in biotin-tagged biomolecule purification.

Is streptavidin used in immunoassays?

Yes, due to its strong biotin affinity.

How is avidin used in egg whites?

As a defense mechanism against bacteria.

Can avidin bind to anything other than biotin?

Its primary specificity is for biotin.

How is streptavidin produced?

Typically through recombinant DNA technology.

Does the glycosylation of avidin affect its use?

Yes, it can lead to nonspecific binding.

Why is streptavidin preferred in some assays?

For its lower non-specific binding and background noise.

Is streptavidin toxic?

No, it’s generally considered non-toxic.

Does streptavidin have a biological role?

It’s less clear, but thought to involve biotin sequestration.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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