Shintani Mami, Tada Minoru, Kobayashi Tetsuo, Kajiho Hiroaki, Kontani Kenji, Katada Toshiaki
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
Biochem Biophys Res Commun. 2007 Jun 8;357(3):661-7. doi: 10.1016/j.bbrc.2007.03.206. Epub 2007 Apr 13.
Rab-family GTPases function as key regulators for membrane traffic. Among them, Rab45/RASEF is an atypical GTPase in that it contains a coiled-coil motif at the mid region and a distinct N-terminal EF-hand domain with C-terminal Rab-homology domain. Here, we provide the initial biochemical characterization and intracellular localization of human Rab45. Rab45 bound guanine nucleotide tri- and di-phosphates through the C-terminal Rab domain. Rab45 was capable of self-interacting, and the self-interaction required the mid region containing the coiled-coil motif. Rab45 expressed in HeLa cells was localized in a small patch in the perinuclear area of the cell, and the localization was regulated by the guanine nucleotide-bound states of Rab45. Interestingly, the mid region, together with Rab domain, appeared to be essential for the characteristic perinuclear localization of Rab45, indicating that the self-interaction may be involved in the intracellular localization of Rab45.
Rab家族GTP酶作为膜运输的关键调节因子发挥作用。其中，Rab45/RASEF是一种非典型GTP酶，因为它在中间区域包含一个卷曲螺旋基序，在N端有一个独特的EF手结构域，在C端有一个Rab同源结构域。在此，我们给出了人Rab45的初步生化特性及细胞内定位。Rab45通过C端Rab结构域结合鸟嘌呤核苷酸三磷酸和二磷酸。Rab45能够自我相互作用，且这种自我相互作用需要包含卷曲螺旋基序的中间区域。在HeLa细胞中表达的Rab45定位于细胞核周围区域的一个小斑块中，且这种定位受Rab45鸟嘌呤核苷酸结合状态的调节。有趣的是，中间区域与Rab结构域一起似乎对Rab45特有的核周定位至关重要，这表明自我相互作用可能参与了Rab45的细胞内定位。
