Futile Encounter Engineering of the DSR-M Dextransucrase Modifies the Resulting Polymer Length

Biochemistry. 2019 Jun 25;58(25):2853-2859. doi: 10.1021/acs.biochem.9b00373. Epub 2019 Jun 7.


The factors that define the resulting polymer length of distributive polymerases are poorly understood. Here, starting from the crystal structure of the dextransucrase DSR-M in complex with an isomaltotetraose, we define different anchoring points for the incoming acceptor. Mutation of one of these, Trp624, decreases the catalytic rate of the enzyme but equally skews the size distribution of the resulting dextran chains toward shorter chains. Nuclear magnetic resonance analysis shows that this mutation influences both the dynamics of the active site and the water accessibility. Monte Carlo simulation of the elongation process allows interpretation of these results in terms of enhanced futile encounters, whereby the less effective binding increases the pool of effective seeds for the dextran chains and thereby directly determines the length distribution of the final polymers.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biocatalysis
  • Catalytic Domain
  • Dextrans / chemistry*
  • Escherichia coli / genetics
  • Glucosyltransferases / chemistry*
  • Glucosyltransferases / genetics
  • Glucosyltransferases / metabolism*
  • Leuconostoc / enzymology
  • Models, Chemical
  • Molecular Structure
  • Monte Carlo Method
  • Mutation
  • Oligosaccharides / chemistry
  • Protein Engineering


  • Dextrans
  • Oligosaccharides
  • isomaltotetraose
  • Glucosyltransferases
  • dextransucrase

Supplementary concepts

  • Leuconostoc citreum