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鏈霉親和素是由什么組成的
2019-06-08 08:26
鏈霉親和素(streptavidin下稱SA)是與親和素(avidin下稱AV)有相似生物學(xué)特性的一種蛋白質(zhì)，是streptomyces avidinii菌的分泌物，其分子量及結(jié)合生物素的能力與雞蛋清中的親和素相似，等電點6.0，非特異性結(jié)合遠比親和素低。
鏈霉親和素分子由4條相同的肽鏈組成，其氨基酸組成中，甘氨酸和丙氨酸的含量較大，而且結(jié)合生物素的活性基團也是肽鏈中的色氨酸殘基；鏈霉親和素是一種稍偏酸性（pH6.0）的蛋白質(zhì)，并且不帶任何糖基。在蛋白水解酶作用下，鏈霉親和素可在N端10～12和C端19-21間斷裂，形成的核心鏈霉親和素仍然保持完整的結(jié)合生物素的能力。鏈霉親和素的活性單位也是以結(jié)合1μg生物素所需的量來表示，1mg鏈霉親和素的最高活性可達18U.
Streptavidin(SA) is a protein that has similar biological properties to avidin(AV). It is a secretion of streptomyces avidini, and its molecular weight and ability to bind biotin are similar to those in egg whites. At 6.0 isoelectric points, the non-specific binding is much lower than the affinity.
Streptomycin molecules consist of four identical peptide chains. In the amino acid composition, the content of Glycine and alanine is relatively large, and the active group that binds to biotin is also the tryptophan residue in the peptide chain.; Streptomycin is a slightly acidic(pH6 .0) protein without any glycosyl group. Under the action of proteolytic enzymes, streptokinin can break between 10-12 at the N end and 19-21 at the C end, and the formed core streptokinin still maintains its complete ability to bind biotin. The active unit of streptomycin is also expressed in the amount required to bind 1 μg biotin, and the maximum activity of 1 mg streptomycin is up to 18U.
Streptavidin(SA) is a protein that has similar biological properties to avidin(AV). It is a secretion of streptomyces avidini, and its molecular weight and ability to bind biotin are similar to those in egg whites. At 6.0 isoelectric points, the non-specific binding is much lower than the affinity.
Streptomycin molecules consist of four identical peptide chains. In the amino acid composition, the content of Glycine and alanine is relatively large, and the active group that binds to biotin is also the tryptophan residue in the peptide chain.; Streptomycin is a slightly acidic(pH6 .0) protein without any glycosyl group. Under the action of proteolytic enzymes, streptokinin can break between 10-12 at the N end and 19-21 at the C end, and the formed core streptokinin still maintains its complete ability to bind biotin. The active unit of streptomycin is also expressed in the amount required to bind 1 μg biotin, and the maximum activity of 1 mg streptomycin is up to 18U.
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