Fukita Y, Mizuta T R, Shirozu M, Ozawa K, Shimizu A, Honjo T
Department of Medical Chemistry, Kyoto University Faculty of Medicine, Japan.
J Biol Chem. 1993 Aug 15;268(23):17463-70.
We have cloned the cDNA encoding the human homologue of S mu bp-2, which binds to single-stranded DNA with 5'-phosphorylated guanine-rich sequences related to the immunoglobulin mu chain switch (S mu) region. The deduced amino acid sequences of the mouse and human S mu bp-2 are 76.5% homologous and contain motifs conserved among helicases. We have identified a domain essential for DNA binding at residues 638-786. The binding domain is less conserved (63% homologous) than the putative catalytic domain of N-terminal half containing most of the helicase motifs (85% homologous). The human and mouse S mu bp-2 have similar, although slightly different, binding specificities. Although the mouse S mu bp-2 preferentially binds to the mouse S mu motif (GGGGT), the human S mu bp-2 binds equally well to the human (GGGCT) and mouse S mu motifs. The human S mu bp-2 gene was mapped to chromosome 11 q13.2-q13.4 by in situ hybridization.
我们克隆了编码人源Sμbp-2同源物的cDNA，该蛋白可与单链DNA结合，其结合序列富含5'-磷酸化鸟嘌呤，与免疫球蛋白μ链开关（Sμ）区域相关。小鼠和人源Sμbp-2的推导氨基酸序列同源性为76.5%，并含有解旋酶中保守的基序。我们确定了638-786位氨基酸残基中对于DNA结合至关重要的结构域。该结合结构域的保守性（同源性63%）低于N端半段推定的催化结构域（同源性85%），后者包含大多数解旋酶基序。人和小鼠的Sμbp-2具有相似但略有不同的结合特异性。虽然小鼠Sμbp-2优先结合小鼠Sμ基序（GGGGT），但人源Sμbp-2与人源（GGGCT）和小鼠Sμ基序的结合能力相当。通过原位杂交将人源Sμbp-2基因定位于11号染色体q13.2-q13.4。
