Authors: Huang, Wen-Chen; Ko, Tzu-Ping¹; Li, Steven S.-L²; Wang, Andrew H.-J.¹

Source: FEBS Journal, Volume 271, Number 20, October 2004 , pp. 4114-4122(9)

Publisher: Wiley-Blackwell

Abstract:

The SUMO proteins are a class of small ubiquitin-like modifiers. SUMO is attached to a specific lysine side chain on the target protein via an isopeptide bond with its C-terminal glycine. There are at least four SUMO proteins in humans, which are involved in protein trafficking and targeting. A truncated human SUMO-2 protein that contains residues 9-93 was expressed in Escherichia coli and crystallized in two different unit cells, with dimensions of a = b = 75.25 Å, c = 29.17 Å and a = b = 74.96 Å, c = 33.23 Å, both belonging to the rhombohedral space group R3. They diffracted X-rays to 1.6 Å and 1.2 Å resolution, respectively. The structures were determined by molecular replacement using the yeast SMT3 protein as a search model. Subsequent refinements yielded R/R_free values of 0.169/0.190 and 0.119/0.185, at 1.6 Å and 1.2 Å, respectively. The peptide folding of SUMO-2 consists of a half-open β-barrel and two flanking α-helices with secondary structural elements arranged as ββαββαβ in the sequence, identical to those of ubiquitin, SMT3 and SUMO-1. Comparison of SUMO-2 with SUMO-1 showed a surface region near the C terminus with significantly different charge distributions. This may explain their distinct intracellular locations. In addition, crystal-packing analysis suggests a possible trimeric assembly of the SUMO-2 protein, of which the biological significance remains to be determined.

Keywords: homology modeling; molecular interactions; protein modification; surface charge distributions; synchrotron radiations

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1432-1033.2004.04349.x

Affiliations: 1: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan 2: Department of Biotechnology, College of Life Sciences, Kaoshiung Medical University, Taiwan

Publication date: 2004-10-01

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