Kassenbrock C K, Kelly R B
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
EMBO J. 1989 May;8(5):1461-7. doi: 10.1002/j.1460-2075.1989.tb03529.x.
Immunoglobulin heavy chain binding protein (BiP/GRP78) is a resident endoplasmic reticulum protein that binds tightly to a number of incompletely assembled or aberrant proteins. BiP also binds ATP and can be purified by ATP affinity chromatography. Here we show that an ATPase activity co-purifies with BiP prepared from canine pancreas. The BiP-associated ATPase has a high affinity for ATP but a low turnover number, suggesting a regulatory, rather than an enzymatic role. We also show that submicromolar levels of ATP or ADP decrease the rate of adsorption of [125I]BiP to nitrocellulose filters coated with protein or non-ionic detergents. In contrast, micromolar levels of AMP increase the rate of adsorption. Furthermore, ATP and ADP decrease the susceptibility of BiP to proteolytic degradation, whereas AMP was found to enhance degradation slightly. Adenine nucleotides may therefore induce or stabilize different conformations of BiP even when ATP hydrolysis does not occur.
免疫球蛋白重链结合蛋白（BiP/GRP78）是一种内质网驻留蛋白，它能与许多未完全组装或异常的蛋白质紧密结合。BiP还能结合ATP，可通过ATP亲和层析法进行纯化。在此我们表明，一种ATP酶活性与从犬胰腺制备的BiP共同纯化。与BiP相关的ATP酶对ATP具有高亲和力，但周转数低，这表明其起调节作用而非酶促作用。我们还表明，亚微摩尔水平的ATP或ADP会降低[125I]BiP吸附到涂有蛋白质或非离子去污剂的硝酸纤维素滤膜上的速率。相反，微摩尔水平的AMP会增加吸附速率。此外，ATP和ADP降低了BiP对蛋白水解降解的敏感性，而发现AMP会略微增强降解。因此，即使不发生ATP水解，腺嘌呤核苷酸也可能诱导或稳定BiP的不同构象。
