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  • The EMBO Journal (2003) 22, 2334 - 2347
  • doi:10.1093/emboj/cdg244

Transcarboxylase 12S crystal structure: hexamer assembly and substrate binding to a multienzyme core

Pamela R. Hall1,2, Yan-Fei Wang1, Rosa E. Rivera-Hainaj3, Xiaojing Zheng3, Marianne Pustai-Carey3, Paul R. Carey3 and Vivien C. Yee1,2,3

  1. Department of Molecular Cardiology and Center for Structural Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
  2. Department of Pharmacology, Case Western Reserve University, Cleveland, OH 44106, USA
  3. Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA

Correspondence to:

Vivien C. Yee, E-mail: yeev@ccf.org

Received 9 January 2003; Accepted 24 March 2003; Revised 20 March 2003

Transcarboxylase from Propionibacterium shermanii is a 1.2 MDa multienzyme complex that couples two carboxylation reactions, transferring CO2- from methylmalonyl-CoA to pyruvate, yielding propionyl-CoA and oxaloacetate. The 1.9 Å resolution crystal structure of the central 12S hexameric core, which catalyzes the first carboxylation reaction, has been solved bound to its substrate methylmalonyl-CoA. Overall, the structure reveals two stacked trimers related by 2-fold symmetry, and a domain duplication in the monomer. In the active site, the labile carboxylate group of methylmalonyl-CoA is stabilized by interaction with the N-termini of two alpha-helices. The 12S domains are structurally similar to the crotonase/isomerase superfamily, although only domain 1 of each 12S monomer binds ligand. The 12S reaction is similar to that of human propionyl-CoA carboxylase, whose beta-subunit has 50% sequence identity with 12S. A homology model of the propionyl-CoA carboxylase beta-subunit, based on this 12S crystal structure, provides new insight into the propionyl-CoA carboxylase mechanism, its oligomeric structure and the molecular basis of mutations responsible for enzyme deficiency in propionic acidemia.

  • Keywords:

    • carboxyl transferase,
    • crystal structure,
    • domain duplication,
    • multienzyme complex,
    • transcarboxylase