Koller-Eichhorn Roland, Marquardt Tobias, Gail Robert, Wittinghofer Alfred, Kostrewa Dirk, Kutay Ulrike, Kambach Christian
Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland.
J Biol Chem. 2007 Jul 6;282(27):19928-37. doi: 10.1074/jbc.M700541200. Epub 2007 Apr 12.
Purine nucleotide-binding proteins build the large family of P-loop GTPases and related ATPases, which perform essential functions in all kingdoms of life. The Obg family comprises a group of ancient GTPases belonging to the TRAFAC (for translation factors) class and can be subdivided into several distinct protein subfamilies. The founding member of one of these subfamilies is the bacterial P-loop NTPase YchF, which had so far been assumed to act as GTPase. We have biochemically characterized the human homologue of YchF and found that it binds and hydrolyzes ATP more efficiently than GTP. For this reason, we have termed the protein hOLA1, for human Obg-like ATPase 1. Further biochemical characterization of YchF proteins from different species revealed that ATPase activity is a general but previously missed feature of the YchF subfamily of Obg-like GTPases. To explain ATP specificity of hOLA1, we have solved the x-ray structure of hOLA1 bound to the nonhydrolyzable ATP analogue AMPPCP. Our structural data help to explain the altered nucleotide specificity of YchF homologues and identify the Ola1/YchF subfamily of the Obg-related NTPases as an exceptional example of a single protein subfamily, which has evolved altered nucleotide specificity within a distinct protein family of GTPases.
嘌呤核苷酸结合蛋白构成了P环GTP酶和相关ATP酶的大家族，它们在所有生命王国中都发挥着重要作用。Obg家族包含一组属于TRAFAC（翻译因子）类的古老GTP酶，可细分为几个不同的蛋白质亚家族。这些亚家族之一的创始成员是细菌P环NTP酶YchF，到目前为止，人们一直认为它作为GTP酶发挥作用。我们对YchF的人类同源物进行了生化特性分析，发现它结合并水解ATP的效率比GTP更高。因此，我们将该蛋白命名为hOLA1，即人类Obg样ATP酶1。对来自不同物种的YchF蛋白进行的进一步生化特性分析表明，ATP酶活性是Obg样GTP酶的YchF亚家族的一个普遍但此前被忽视的特征。为了解释hOLA1的ATP特异性，我们解析了与不可水解的ATP类似物AMPPCP结合的hOLA1的X射线结构。我们的结构数据有助于解释YchF同源物改变的核苷酸特异性，并将Obg相关NTP酶的Ola1/YchF亚家族确定为单个蛋白质亚家族的一个特殊例子，该亚家族在一个独特的GTP酶蛋白质家族中进化出了改变的核苷酸特异性。
