The 1.9 Å structure of the branched-chain amino-acid transaminase (IlvE) from Mycobacterium tuberculosis

L. W. Tremblay, John S. Blanchard

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Unlike mammals, bacteria encode enzymes that synthesize branched-chain amino acids. The pyridoxal 5′-phosphate-dependent transaminase performs the final biosynthetic step in these pathways, converting keto acid precursors into - amino acids. The branched-chain amino-acid transaminase from Mycobacterium tuberculosis (MtIlvE) has been crystallized and its structure has been solved at 1.9 Å resolution. The MtIlvE monomer is composed of two domains that interact to form the active site. The biologically active form of IlvE is a homodimer in which each monomer contributes a substrate-specificity loop to the partner molecule. Additional substrate selectivity may be imparted by a conserved N-terminal Phe30 residue, which has previously been observed to shield the active site in the type IV fold homodimer. The active site of MtIlvE contains density corresponding to bound PMP, which is likely to be a consequence of the presence of tryptone in the crystallization medium. Additionally, two cysteine residues are positioned at the dimer interface for disulfide-bond formation under oxidative conditions. It is unknown whether they are involved in any regulatory activities analogous to those of the human mitochondrial branched-chain amino-acid transaminase.

Original languageEnglish (US)
Pages (from-to)1071-1077
Number of pages7
JournalActa Crystallographica Section F: Structural Biology and Crystallization Communications
Volume65
Issue number11
DOIs
StatePublished - 2009

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tuberculosis
Mycobacterium tuberculosis
amino acids
Catalytic Domain
Monomers
Keto Acids
Branched Chain Amino Acids
Pyridoxal Phosphate
Mammals
Substrates
Crystallization
Transaminases
Disulfides
Dimers
Cysteine
Bacteria
monomers
Substrate Specificity
Amino Acids
mammals

Keywords

  • Branched-chain amino acids
  • Mycobacterium tuberculosis
  • Pyridoxal 5′-phosphate
  • Pyridoxamine 5′-phosphate
  • Transaminases

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Structural Biology
  • Genetics
  • Condensed Matter Physics
  • Medicine(all)

Cite this

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abstract = "Unlike mammals, bacteria encode enzymes that synthesize branched-chain amino acids. The pyridoxal 5′-phosphate-dependent transaminase performs the final biosynthetic step in these pathways, converting keto acid precursors into - amino acids. The branched-chain amino-acid transaminase from Mycobacterium tuberculosis (MtIlvE) has been crystallized and its structure has been solved at 1.9 {\AA} resolution. The MtIlvE monomer is composed of two domains that interact to form the active site. The biologically active form of IlvE is a homodimer in which each monomer contributes a substrate-specificity loop to the partner molecule. Additional substrate selectivity may be imparted by a conserved N-terminal Phe30 residue, which has previously been observed to shield the active site in the type IV fold homodimer. The active site of MtIlvE contains density corresponding to bound PMP, which is likely to be a consequence of the presence of tryptone in the crystallization medium. Additionally, two cysteine residues are positioned at the dimer interface for disulfide-bond formation under oxidative conditions. It is unknown whether they are involved in any regulatory activities analogous to those of the human mitochondrial branched-chain amino-acid transaminase.",
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