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|1zwv, 20 NMR models ()|
Solution Structure of the subunit binding domain (hbSBD) of the human mitochondrial branched-chain alpha-ketoacid dehydrogenase
The homo-24-meric dihydrolipoyl transacylase (E2) scaffold of the human branched-chain alpha-ketoacid dehydrogenase complex (BCKDC) contains the lipoyl-bearing domain (hbLBD), the subunit-binding domain (hbSBD) and the inner core domain that are linked to carry out E2 functions in substrate channeling and recognition. In this study, we employed NMR techniques to determine the structure of hbSBD and dynamics of several truncated constructs from the E2 component of the human BCKDC, including hbLBD (residues 1-84), hbSBD (residues 111-149), and a di-domain (hbDD) (residues 1-166) comprising hbLBD, hbSBD and the interdomain linker. The solution structure of hbSBD consists of two nearly parallel helices separated by a long loop, similar to the structures of the SBD isolated from other species, but it lacks the short 3(10) helix. The NMR results show that the structures of hbLBD and hbSBD in isolated forms are not altered by the presence of the interdomain linker in hbDD. The linker region is not entirely exposed to solvent, where amide resonances associated with approximately 50% of the residues are observable. However, the tethering of these two domains in hbDD significantly retards the overall rotational correlation times of hbLBD and hbSBD, changing from 5.54 ns and 5.73 ns in isolated forms to 8.37 ns and 8.85 ns in the linked hbDD, respectively. We conclude that the presence of the interdomain linker restricts the motional freedom of the hbSBD more significantly than hbLBD, and that the linker region likely exists as a soft rod rather than a flexible string in solution.
Structure of the subunit binding domain and dynamics of the di-domain region from the core of human branched chain alpha-ketoacid dehydrogenase complex., Chang CF, Chou HT, Lin YJ, Lee SJ, Chuang JL, Chuang DT, Huang TH, J Biol Chem. 2006 Sep 22;281(38):28345-53. Epub 2006 Jul 20. PMID:016861235
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
[ODB2_HUMAN] Defects in DBT are the cause of maple syrup urine disease type 2 (MSUD2) [MIM:248600]. MSUD is an autosomal recessive disorder characterized by mental and physical retardation, feeding problems, and a maple syrup odor to the urine.
[ODB2_HUMAN] The branched-chain alpha-keto dehydrogenase complex catalyzes the overall conversion of alpha-keto acids to acyl-CoA and CO(2). It contains multiple copies of three enzymatic components: branched-chain alpha-keto acid decarboxylase (E1), lipoamide acyltransferase (E2) and lipoamide dehydrogenase (E3).
About this Structure
- ↑ Fisher CW, Lau KS, Fisher CR, Wynn RM, Cox RP, Chuang DT. A 17-bp insertion and a Phe215----Cys missense mutation in the dihydrolipoyl transacylase (E2) mRNA from a thiamine-responsive maple syrup urine disease patient WG-34. Biochem Biophys Res Commun. 1991 Jan 31;174(2):804-9. PMID:1847055
- ↑ Tsuruta M, Mitsubuchi H, Mardy S, Miura Y, Hayashida Y, Kinugasa A, Ishitsu T, Matsuda I, Indo Y. Molecular basis of intermittent maple syrup urine disease: novel mutations in the E2 gene of the branched-chain alpha-keto acid dehydrogenase complex. J Hum Genet. 1998;43(2):91-100. PMID:9621512 doi:10.1007/s100380050047