Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 337, Issue 3, Pages 761-770Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2004.01.047
Keywords
GTP-binding protein; GTPase; Obg; Ras; EF-Tu
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Obg comprises a unique family of high-molecular mass GTPases conserved from bacteria to eukaryotes. Bacterial Obg is essential for cellular growth, sporulation, and differentiation. Here, we report the crystal structure of the full-length form of Obg from Thermus thermophilus HB8 at 2.07 Angstrom resolution, in the nucleotide-free state. It reveals a three-domain arrangement, composed of the N-terminal domain, the guanine nucleotide-binding domain (G domain), and the C-terminal domain. The N-terminal and G domains have the Obg fold and the Ras-like fold, respectively. These global folds are similar to those of the recently published structure of the C-terminal domain-truncated form of Obg from Bacillus subtilis. On the other hand, the C-terminal domain of Obg was found to have a novel fold (the OCT fold). A comparison of the T. thermophilus and B. subtilis nucleotide-free Obg structures revealed significant conformational changes in the switch-I and switch-II regions of the G domain. Notably, the N-terminal domain is rotated drastically, by almost 180degrees, around the G domain axis. In the T thermophilus Obg crystal, the nucleotide-binding site of the G domain interacts with the C-terminal domain of the adjacent molecule. These data suggest a possible domain rearrangement of Obg, and a potential role of the C-terminal domain in the regulation of the nucleotide-binding state. (C) 2004 Elsevier Ltd. All rights reserved.
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