The ubiquitin-like (Ubl) system has been shown to be ubiquitous in all three kingdoms of life following the very recent characterization of ubiquitin-like small archaeal modifier proteins (SAMP1 and 2) from Haloferax volcanii. The ubiquitin (Ub) and Ubl molecules in eukaryotes have been studied extensively and their cellular functions are well established. Biochemical and structural data pertaining to prokaryotic Ubl protein (Pup) continue to be reported. In contrast to eukaryotes and prokaryotes, no structural information on the archaeal Ubl molecule is available. Here we determined the crystal structure of SAMP1 at 1.55. Å resolution and generated a model of SAMP2. These were then compared with other Ubl molecules from eukaryotes as well as prokaryotes. The structure of SAMP1 shows a β-grasp fold of Ub, suggesting that the archaeal Ubl molecule is more closely related to eukaryotic Ub and Ubls than to its prokaryotic counterpart. The current structure identifies the location of critical elements such a single lysine residue (Lys4), C-terminal di-glycine motif, hydrophobic patches near leucine 60, and uniquely inserted α-helical segments (α1 and α3) in SAMP1. Based on the structure of SAMP1, several Ub-like features of SAMPs such as poly-SAMPylation and non-covalent interactions have been proposed, which should provide the basis for further investigations concerning the molecular function of archaeal Ubls and the large super-family of β-grasp fold proteins in the archaeal kingdom.
|Number of pages
|Biochemical and biophysical research communications
|Published - 2011 Feb 4
Bibliographical noteFunding Information:
We thank the staff at 6C beamline, Pohang Light Source, Korea and AR-NE3 beamline, Photon Factory, Japan for helping with the data collection. This work was supported by WCU (World Class University) program (R33-10108) through the National Research Foundation and a Korea Research Foundation Grant (KRF-2007-314-C00176) funded by the Ministry of Education, Science and Technology, and the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare and Family Affairs, Republic of Korea (A092006).
- Haloferax volcanii
- β-Grasp fold
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology