Streptavidin Protein
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Description
Product Specs
Product Science Overview
Streptavidin is a tetrameric protein, meaning it is composed of four identical subunits. Each subunit has a molecular weight of approximately 13 kDa, resulting in a total molecular weight of around 52 kDa for the tetramer . The protein’s secondary structure consists of eight antiparallel β-strands that fold into a β-barrel tertiary structure. The biotin-binding site is located at one end of each β-barrel .
The tetrameric structure of streptavidin allows it to bind up to four biotin molecules simultaneously. The binding pocket for biotin is highly complementary in shape and forms an extensive network of hydrogen bonds with biotin, contributing to the high affinity of the interaction . The dissociation constant (K_d) for the streptavidin-biotin interaction is on the order of 10^-14 mol/L, making it one of the strongest known non-covalent interactions .
Streptavidin’s high affinity for biotin makes it an invaluable tool in various applications, including:
- Molecular Biology: Streptavidin is used to purify biotinylated molecules, such as nucleic acids and proteins, through affinity chromatography. This allows for the isolation of specific molecules from complex mixtures .
- Immunoassays: In techniques like ELISA (enzyme-linked immunosorbent assay), streptavidin is used to detect biotinylated antibodies or antigens, enhancing the sensitivity and specificity of the assay .
- Fluorescence Imaging: Streptavidin conjugated to fluorophores is used in fluorescence microscopy to detect biotinylated targets, providing signal amplification for medium- and low-abundance targets .
- Bionanotechnology: Streptavidin-biotin interactions are utilized in the construction of nanoscale devices and materials, leveraging the strong and specific binding properties of the complex .
One of the main advantages of streptavidin is its non-glycosylated nature, which reduces nonspecific binding compared to other biotin-binding proteins like avidin . This makes streptavidin particularly useful in applications where low background signals are crucial.
However, the presence of endogenous biotin in mammalian cells and tissues can lead to background signals in certain applications. To mitigate this, blocking kits are available to reduce nonspecific binding caused by endogenous biotin .
