Active site identification through geometry-based and sequence profile-based calculations: burial of catalytic clefts

J Mol Biol. 2005 Jun 10;349(3):547-57. doi: 10.1016/j.jmb.2005.04.018. Epub 2005 Apr 25.

Abstract

Electrostatics calculations with proteins that are uniformly charged over volume can aid enzyme/non-enzyme discrimination. For known enzymes, such methods locate active sites to within 5% on the enzyme surface, in 77% of a test set. We now report that removing the dielectric boundary improves active site location to 80%, with optimal discrimination between enzymes and non-enzymes of around 80% specificity and 80% sensitivity. This calculation quantifies burial of solvent-accessible regions. Many of the true enzymes incorrectly assigned as non-enzymes have active sites at subunit boundaries. These are missed in monomer-based calculations. Catalytic and non-catalytic antibodies are studied in this context of active/binding site burial. Whilst catalytic antibodies, on average, have marginally higher active site burial than non-catalytic antibodies, these values are generally smaller than for non-antibody enzymes, possibly contributing to their relatively low turnover. Prediction of active site location improves further when sequence profile-based weights replace the uniform charge distribution, so that a combination of burial and amino acid conservation is assessed. Accuracy rises to 93% of active sites to within 5%, in the test set, for the optimal profile weights scheme. The equivalent value in a separate validation set is 89% to within 5%. Enzyme/non-enzyme and enzyme functional site predictions are made for structural genomics proteins, suggesting that a substantial majority of these are non-enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies / chemistry
  • Antibodies / physiology*
  • Catalytic Domain / physiology*
  • Enzymes / chemistry
  • Enzymes / physiology*
  • Genomics
  • Sequence Analysis, Protein*

Substances

  • Antibodies
  • Enzymes