Streptomyces avidinii

Avidin-biotin complex (ABC) is based on the high affinity that streptavidin (from Streptomyces avidinii) and avidin (from chicken egg) have for biotin. Biotin is a naturally occurring vitamin. One mole avidin will bind four moles biotin. ABC method affords a several-fold higher antigen detectability than those achieved in the standard indirect method. 

Strepavidin A 60 kD extracellular protein of Streptomyces avidinii with four high-affinity biotin binding sites. Unlike avidin, streptavidin has a near neutral isoelectric point and is free of carbohydrate side chains. 

Avidin is a glycoprotein which was initially extracted from chicken egg white and which exhibits four deep binding pockets for biotin. Streptavidin is an analogous protein with a molecular weight of about 70 kD which is prepared from the recombinant bacteria strain Streptomyces avidinii and which... 

A biochemical curiosity is the presence in egg white of the glycoprotein avidin.ab Each 68-kDa subunit of this tetrameric protein binds one molecule of biotin tenaciously with Kf 1015 M 1. Nature s purpose in placing this unusual protein in egg white is uncertain. Perhaps it is a storage form of biotin, but it is more likely an antibiotic that depletes the environment of biotin. A closely similar protein streptavidin is secreted into the culture medium by Streptomyces avidinii.c Its sequence is homologous to that of avidin. It has a similar binding constant for biotin and the two proteins have similar three-dimensional structures.3/d i Biotin binds at one end of a P barrel formed from antiparallel strands and is held by multiple hydrogen bonds and a conformational alteration that allows a peptide loop to close over the bound vitamin. 

Streptavidin is another biotin binding protein isolated from Streptomyces avidinii that can overcome some of the nonspecificities of avidin (Chaiet and Wolf, 1964). Similar to avidin, streptavidin contains four subunits, each with a single biotin binding site. After some postsecretory modifications, the intact tetrameric protein has a molecular mass of about 60,000 D, slightly less than that of avidin (Bayer et al., 1986, 1989). 

The most commonly used protein, often ultilized as a versatile supramolecular building block for the synthesis of biohybrid materials, is probably streptavidin. Streptavidin was discovered in the bacterium Streptomyces avidinii 241-242-243 and is an homo-tetrameric protein with a 2-fold symmetry, and molecular weight of 60 kDa.244,245,246... 

Streptavidin (from Streptomyces avidinii) and avidin (from chicken egg) both possess four binding sites for biotin. The biotin molecule is easily conjugated to antibodies and enzymes. In the avidin-biotin complex (ABC) method secondary antibodies are conjugated to biotin and function as links between tissue-bound primary antibodies and an avidin-biotin-peroxidase complex (5). 

Yet another variation of the Western blot exploits the strong interaction between biotin and streptavidin. Biotin is a 244-Da vitamin found in all cells (Fig. 18-4). Streptavidin is a 75-kDa, tetrameric protein isolated from Streptomyces avidinii. Each streptavidin monomer is capable of binding a single molecule of biotin. The dissociation constant of the streptavidin/biotin complex is on the order of 10-1S M, one of the strongest noncovalent interactions found in nature. Many reagents are commercially... 

Streptomyces avidinii can be obtained from the American Type Culture Collection (ATCC 27419) and grown in a medium according to Stapley et al. (1963) on 2% agar plates at 30"C. Spores from four plates are used to inoculate 4 1 of medium, which is then incubated for 3 days at 30 C. The medium is clarified by centrifugation (10 min, 10000 xg) and concentrated in an Amicon concentrator (PM 10 membrane) to 400 ml. To this solution at 0"C, (NH4)2S04... 

Similarly, streptavidin from Streptomyces avidinii - and also its eukaryotic counterpart avidin, which occurs in chicken egg white - has evolved only in order to tightly complex biotin, a small vitamin compound [15]. In this case the complexation is kinetically almost irreversible, which makes sense for its role as a bacterial antibiotic protein and has led to its widespread use as a biochemical reagent (for references, see [16]). 

Streptomyces avidinii 511 Streptomyces coelicolor 1823 Streptomyces lividans 1824 Streptomyces peucetius 1804 Stromal antigen 1281 stRNA (small temporal RNA) 628 StSNl 485 StSN2 485... 

Avidin - an egg white protein or as a streptavidin from Streptomyces avidinii bacteria that has four extremely high-affinity-binding sites for biotin. 

Streptavidin, a tetrameric protein (Mr 60 kDa) from Streptomyces avidinii with a high affinity to biotin (fC 10 M). Streptavidin is used in various laboratory techniques for detecting biotinylated molecules, and is preferred to avidin due to its more favorable isoelectric point and lack of glycosylation. It belongs to the protein superfamily calycins [N. M. Green, Methods Enzymol. 1990, 184, 51 S. Freitag et al.. Protein Sci. 1997, 6, 1157 A. Skerra, T. G. Schmidt, Methods Enzymol. 2000, 326, 271]. 

Streptavidin. A tetrameric protein (Mr 60000) from Streptomyces avidinii which, in contrast to avidin (see there), has no glycoprotein part. It has an appreciably lower isoelectric point (IP=5.0) than avidin. Substitution of avidin by S. can in some cases markedly reduce non-speciflc conditions. 

Avidin (occurring in eggs) or streptavidin (produced by Streptomyces avidinii) are usually tetrameric proteins, where each subunit has very high affinity to bind biotin (vitamin B7). The formation constants lie between 10 " and 10 which can be classified as the strongest noncovalent bonds. Thus, biotinylated conjugates can be easily bound to avidin-modified counter-partners and surfaces. 

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