Shimizu K, Shirataki H, Honda T, Minami S, Takai Y
Department of Molecular Biology and Biochemistry, Osaka University Medical School, Suita 565, Japan.
J Biol Chem. 1998 Mar 20;273(12):6591-4. doi: 10.1074/jbc.273.12.6591.
We have recently isolated SMAP (Smg GDS-associated protein; Smg GDS: small G protein GDP dissociation stimulator) as a novel Smg GDS-associated protein, which has Armadillo repeats and is phosphorylated by Src tyrosine kinase. SMAP is a human counterpart of mouse KAP3 (kinesin superfamily-associated protein) that is associated with mouse KIF3A/B (a kinesin superfamily protein), which functions as a microtubule-based ATPase motor for organelle transport. We isolated here a SMAP-interacting protein from a human brain cDNA library, identified it to be a human homolog of Xenopus XCAP-E (Xenopus chromosome-associated polypeptide), a subunit of condensins that regulate the assembly and structural maintenance of mitotic chromosomes, and named it HCAP (Human chromosome-associated polypeptide). Tissue and subcellular distribution analyses indicated that HCAP was ubiquitously expressed and highly concentrated in the nuclear fraction, where SMAP and KIF3B were also present. SMAP was extracted as a ternary complex with HCAP and KIF3B from the nuclear fraction in the presence of Mg-ATP. The results suggest that SMAP/KAP3 serves as a linker between HCAP and KIF3A/B in the nucleus, and that SMAP/KAP3 plays a role in the interaction of chromosomes with an ATPase motor protein.
我们最近分离出SMAP（Smg GDS相关蛋白；Smg GDS：小G蛋白GDP解离刺激因子）作为一种新型的Smg GDS相关蛋白，它具有犰狳重复序列且被Src酪氨酸激酶磷酸化。SMAP是小鼠KAP3（驱动蛋白超家族相关蛋白）的人类对应物，小鼠KAP3与小鼠KIF3A/B（一种驱动蛋白超家族蛋白）相关联，后者作为基于微管的ATP酶马达参与细胞器运输。我们在此从人脑cDNA文库中分离出一种与SMAP相互作用的蛋白，鉴定其为非洲爪蟾XCAP - E（非洲爪蟾染色体相关多肽）的人类同源物，XCAP - E是凝缩蛋白的一个亚基，参与调控有丝分裂染色体的组装和结构维持，我们将其命名为HCAP（人类染色体相关多肽）。组织和亚细胞分布分析表明，HCAP广泛表达且高度集中在核组分中，SMAP和KIF3B也存在于该组分中。在Mg - ATP存在的情况下，SMAP以与HCAP和KIF3B的三元复合物形式从核组分中被提取出来。结果表明，SMAP/KAP3在细胞核中作为HCAP和KIF3A/B之间的连接物，并且SMAP/KAP3在染色体与ATP酶马达蛋白的相互作用中发挥作用。
