Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 419, Issue 2, Pages 160-164Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2012.01.125
Keywords
LeuD; 3-Isopropylmalate isomerase; 3-lsopropylmalate dehydratase; Small subunit; Broad specificity; Crystal structure
Categories
Funding
- National Research Foundation [NRF-M1AXA002-20110028397]
- Ministry of Education, Science and Technology of Korea
- Functional Proteomics Center
- Korea Ministry of Science and Technology
- KIST
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3-Isopropylmalate/citramalate (IPM) isomerase catalyzes the second step in the leucine biosynthesis pathway. IPM isomerase from Methanococcus jannaschii is a complex protein consisting of a large (MjLeuC) and a small subunit (MjLeuD). It has broad substrate specificity, unlike other bacterial IPM isomerases. In order to understand the reasons for this broad substrate specificity, we determined the crystal structure of MjLeuD at a resolution of 2.0 angstrom. The asymmetric unit contained 6 molecules of LeuD, including three homodimers. The overall structure had a beta/beta/alpha sandwich-fold consisting of 8 alpha-helices and 7 beta-strands. The C-terminal helix, which is important in homodimer formation, showed conformational differences between two homodimer forms of MjLeuD. In addition, we identified a hydrophobic residue (Val28) near the substrate recognition region that may explain the broad substrate specificity of IPM isomerase. Therefore, we suggest that LeuD proteins can be divided into 2 subfamilies, LeuD subfamilies 1 and 2, which show differences in overall structure and in the substrate recognition region. (C) 2012 Elsevier Inc. All rights reserved.
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