Devi Seenivasan Karthiga, Chichili Vishnu Priyanka Reddy, Jeyakanthan J, Velmurugan D, Sivaraman J
Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Chennai 600 025, India.
Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
J Struct Biol. 2015 Jun;190(3):367-72. doi: 10.1016/j.jsb.2015.04.012. Epub 2015 Apr 24.
ATP-binding cassette (ABC) transporters are a major family of small molecule transporter proteins, and their deregulation is associated with several diseases, including cancer. Here, we report the crystal structure of the nucleotide binding domain (NBD) of an amino acid ABC transporter from Thermus thermophilus (TTHA1159) in its apo form and as a complex with ADP along with functional studies. TTHA1159 is a putative arginine ABC transporter. The apo-TTHA1159 was crystallized in dimeric form, a hitherto unreported form of an apo NBD. Structural comparison of the apo and ADP-Mg(2+) complexes revealed that Phe14 of TTHA1159 undergoes a significant conformational change to accommodate ADP, and that the bound ADP interacts with the P-loop (Gly40-Thr45). Modeling of ATP-Mg(2+):TTHA1159 complex revealed that Gln86 and Glu164 are involved in water-mediated hydrogen bonding contacts and Asp163 in Mg(2+) ion-mediated hydrogen bonding contacts with the γ-phosphate of ATP, consistent with the findings of other ABC transporters. Mutational studies confirmed the necessity of each of these residues, and a comparison of the apo/ADP Mg(2+):TTHA1159 with its ATP-complex model suggests the likelihood of a key conformational change to the Gln86 side chain for ATP hydrolysis.
ATP结合盒（ABC）转运蛋白是小分子转运蛋白的一个主要家族，其失调与包括癌症在内的多种疾病相关。在此，我们报告嗜热栖热菌（Thermus thermophilus）氨基酸ABC转运蛋白（TTHA1159）的核苷酸结合结构域（NBD）的无配体形式以及与ADP形成复合物的晶体结构，并进行功能研究。TTHA1159是一种假定的精氨酸ABC转运蛋白。无配体的TTHA1159以二聚体形式结晶，这是一种迄今未报道的无配体NBD形式。无配体和ADP-Mg(2+)复合物的结构比较表明，TTHA1159的Phe14发生显著构象变化以容纳ADP，且结合的ADP与P环（Gly40-Thr45）相互作用。ATP-Mg(2+):TTHA1159复合物的建模显示，Gln86和Glu164参与与ATP的γ-磷酸基团的水介导氢键接触，而Asp163参与Mg(2+)离子介导的氢键接触，这与其他ABC转运蛋白的研究结果一致。突变研究证实了这些残基各自的必要性，将无配体/ADP Mg(2+):TTHA1159与其ATP复合物模型进行比较表明，Gln86侧链发生关键构象变化以进行ATP水解的可能性。
