Rimm D L, Pollard T D
Department of Cell Biology and Anatomy, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
J Cell Biol. 1989 Aug;109(2):585-91. doi: 10.1083/jcb.109.2.585.
Immunolocalization of monoclonal antibodies to Acanthamoeba myosin I showed a cross-reactive protein in nuclei (Hagen, S. J., D. P. Kiehart, D. A. Kaiser, and T. D. Pollard. 1986. J. Cell Biol. 103:2121-2128). This protein is antigenically related to myosin I in that nine monoclonal antibodies and three polyclonal antibodies are cross-reactive. However, studies with affinity-purified antibodies and two-dimensional peptide maps show that the protein is not a proteolytic product of myosin I. We have used cell fractionation and column chromatography to purify this protein. It is a dimer of 34-kD polypeptides with a Stokes' radius of 4 nm. A polyclonal antisera generated against the purified protein confirms the nuclear localization seen with the cross-reactive monoclonal antibodies. The 34-kD protein binds actin filaments in an ATP-insensitive manner with a Kd of approximately 0.25 microM without cross-linking, severing, or capping. No ATPase activity was detected in the presence or absence of actin. It also binds to DNA. These unique properties suggest we have discovered a new class of actin-binding protein. We have given this protein the name NAB for "nuclear actin-binding" protein.
针对棘阿米巴肌球蛋白I的单克隆抗体的免疫定位显示，在细胞核中有一种交叉反应蛋白（哈根，S. J.，D. P. 基哈特，D. A. 凯泽和T. D. 波拉德。1986年。《细胞生物学杂志》103:2121 - 2128）。这种蛋白在抗原性上与肌球蛋白I相关，因为有九种单克隆抗体和三种多克隆抗体具有交叉反应性。然而，用亲和纯化抗体和二维肽图进行的研究表明，该蛋白不是肌球蛋白I的蛋白水解产物。我们已使用细胞分级分离和柱色谱法纯化这种蛋白。它是一种由34-kD多肽组成的二聚体，斯托克斯半径为4纳米。针对纯化蛋白产生的多克隆抗血清证实了交叉反应性单克隆抗体所显示的核定位。这种34-kD蛋白以一种对ATP不敏感的方式结合肌动蛋白丝，解离常数约为0.25微摩尔，且不发生交联、切断或封端。无论有无肌动蛋白，均未检测到ATP酶活性。它也与DNA结合。这些独特的特性表明我们发现了一类新的肌动蛋白结合蛋白。我们将这种蛋白命名为NAB，即“核肌动蛋白结合”蛋白。
