链霉亲和素分子由4条相同的肽链组成，其氨基酸组成中，甘氨酸和丙氨酸的含量较大，而且结合生物素的活性基团也是肽链中的色氨酸残基；

链霉亲和素是一种稍偏酸性（pH6.0）的蛋白质，并且不带任何糖基。

在蛋白水解酶作用下，链霉亲和素可在N端10～12和C端19-21间断裂，形成的核心链霉亲和素仍然保持完整的结合生物素的能力，所以可以提高融合率。

链霉亲和素是与亲和素有相似生物学特性的一种蛋白质，是链霉菌的分泌物，其分子量及结合生物素的能力与鸡蛋清中的亲和素相似，等电点6.0，非特异性结合远比亲和素低。

Streptavidin molecule is composed of four identical peptide chains. In its amino acid composition, the contents of glycine and alanine are large, and the active group binding biotin is also tryptophan residue in the peptide chain;

Streptavidin is a slightly acidic (pH 6.0) protein without any sugar groups.

Under the action of proteolytic enzyme, streptavidin can break between N-terminal 10-12 and C-terminal 19-21, and the formed core streptavidin still maintains the complete ability to bind biotin, so the fusion rate can be improved.

Streptavidin is a protein with similar biological characteristics to avidin. It is the secretion of Streptomyces. Its molecular weight and ability to bind biotin are similar to avidin in egg white. Its isoelectric point is 6.0, and its nonspecific binding is much lower than avidin.