Miyata Y, Yahara I
Department of Cell Biology, Tokyo Metropolitan Institute of Medical Science, Japan.
Biochemistry. 1995 Jun 27;34(25):8123-9. doi: 10.1021/bi00025a019.
Purified casein kinase II (CKII) aggregates and loses activity under physiological salt conditions and within the range of physiological temperatures. In accord with our previous report [Miyata, Y., & Yahara, I. (1992) J. Biol. Chem. 267, 7042-7047], we report here that HSP90 protects CKII from the aggregation and inactivation by forming soluble CKII-HSP90 complexes. Surface plasmon resonance (SPR) measurements revealed that CKII binds to immobilized HSP90 within minutes. The KD of the binding is approximately 10(-7) M. ATP does not influence the interaction. The membrane-overlay method revealed that HSP90 binds to the catalytic CKII alpha subunit. Heparin, which binds to CKII alpha, inhibited the binding of CKII to HSP90-Sepharose. In addition, HSP90 competed with DNA for binding to CKII. Finally, SPR experiments showed that a peptide corresponding to the heparin and DNA binding site of CKII alpha binds to immobilized HSP90. These results indicate that HSP90, DNA, and heparin compete with each other for binding to a common site of CKII alpha. If the binding of CKII to DNA is biologically significant, it could be possibly regulated also by HSP90.
纯化的酪蛋白激酶II（CKII）在生理盐浓度条件下及生理温度范围内会发生聚集并失去活性。与我们之前的报道[Miyata, Y., & Yahara, I. (1992) J. Biol. Chem. 267, 7042 - 7047]一致，我们在此报道，热休克蛋白90（HSP90）通过形成可溶性的CKII - HSP90复合物，保护CKII不发生聚集和失活。表面等离子体共振（SPR）测量显示，CKII在数分钟内就能与固定化的HSP90结合。结合的解离常数（KD）约为10^(-7) M。ATP不影响这种相互作用。膜覆盖法显示，HSP90与具有催化活性的CKIIα亚基结合。能与CKIIα结合的肝素抑制了CKII与HSP90 - 琼脂糖的结合。此外，HSP90与DNA竞争结合CKII。最后，SPR实验表明，一段与CKIIα的肝素和DNA结合位点对应的肽段能与固定化的HSP90结合。这些结果表明，HSP90、DNA和肝素相互竞争结合CKIIα的同一个位点。如果CKII与DNA的结合具有生物学意义，那么它也可能受到HSP90的调控。
