Jong A Y, Aebersold R, Campbell J L
J Biol Chem. 1985 Dec 25;260(30):16367-74.
DNA affinity chromatography has been used to identify the major single-stranded nucleic acid binding proteins (SSBs) of Saccharomyces cerevisiae. There are five abundant species having molecular masses of 50, 45, 31, 23, and 20 kDa. Four of these proteins are cytoplasmic and one is mitochondrial. To date, three of the proteins have been purified to homogeneity. The purified proteins are designated SSB-m, SSB-1, and SSB-2, with molecular masses of 20, 45, and 50 kDa, respectively. SSB-m is found only in mitochondrial subcellular fractions. SSB-1 stimulates purified yeast DNA polymerase I, while SSB-2 inhibits DNA polymerase I. An antibody against SSB-1 has been prepared in rabbits and purified by SSB-1-Sepharose affinity chromatography. The purified antibody specifically inhibits DNA synthesis in an in vitro replication system, suggesting that SSB-1 may be involved in DNA replication in vivo. SSB-2 has the highest affinity for single-stranded DNA of all three proteins. It may represent a new class of eukaryotic SSB, on the basis of molecular weight, inhibition of DNA polymerase and antigenicity. Antibodies have also been prepared against SSB-2. The immunological reagents have been used to show that SSB-1, SSB-2, and SSB-m are antigenically distinct, as well as to study the relationship of these three SSBs to other proteins in yeast.
DNA亲和层析已被用于鉴定酿酒酵母的主要单链核酸结合蛋白（SSB）。有5种丰富的蛋白，分子量分别为50、45、31、23和20 kDa。其中4种蛋白位于细胞质中，1种位于线粒体中。到目前为止，已有3种蛋白被纯化至同质。纯化后的蛋白分别命名为SSB-m、SSB-1和SSB-2，分子量分别为20、45和50 kDa。SSB-m仅存在于线粒体亚细胞组分中。SSB-1可刺激纯化的酵母DNA聚合酶I，而SSB-2则抑制DNA聚合酶I。已用兔制备了抗SSB-1的抗体，并通过SSB-1-琼脂糖亲和层析进行纯化。纯化后的抗体在体外复制系统中特异性抑制DNA合成，这表明SSB-1可能参与体内DNA复制。在所有这三种蛋白中，SSB-2对单链DNA的亲和力最高。基于分子量、对DNA聚合酶的抑制作用和抗原性，它可能代表一类新的真核生物SSB。也已制备了抗SSB-2的抗体。这些免疫试剂已被用于证明SSB-1、SSB-2和SSB-m在抗原性上是不同的，同时也用于研究这三种SSB与酵母中其他蛋白的关系。
