Structural and biochemical characterization of MCAT from photosynthetic microorganism Synechocystis sp. PCC 6803 reveal its stepwise catalytic mechanism

Biochem Biophys Res Commun. 2015 Feb 13;457(3):398-403. doi: 10.1016/j.bbrc.2015.01.003. Epub 2015 Jan 9.


Malonyl-coenzyme A: acyl-carrier protein transacylase (MCAT) catalyzes the transfer of malonyl group from malonyl-CoA to the holo-acyl carrier protein (Holo-ACP), yielding malonyl-ACP. The overall reaction has been extensively studied in heterotrophic microorganisms, while its mechanism in photosynthetic autotrophs as well as the stepwise reaction information remains unclear. Here the 2.42 Å crystal structure of MCAT from photosynthetic microorganism Synechocystis sp. PCC 6803 is presented. It demonstrates that Arg113, Ser88 and His188 constitute catalytic triad. The second step involved ACP-MCAT-malonyl intermediate is speed-limited instead of the malonyl-CoA-MCAT intermediate in the first step. Therefore His87, Arg113 and Ser88 render different contributions for the two intermediates. Additionally, S88T mutant initializes the reaction by H87 deprotonating S88T which is different from the wild type.

Keywords: Intermediate; MCAT; Structure; Synechocystis sp. PCC 6803.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl-Carrier Protein S-Malonyltransferase / chemistry*
  • Acyl-Carrier Protein S-Malonyltransferase / genetics
  • Acyl-Carrier Protein S-Malonyltransferase / metabolism*
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Catalysis
  • Catalytic Domain
  • Conserved Sequence
  • Crystallography, X-Ray
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Conformation
  • Sequence Homology, Amino Acid
  • Synechocystis / enzymology*
  • Synechocystis / genetics


  • Bacterial Proteins
  • Acyl-Carrier Protein S-Malonyltransferase