title: Protein knots and fold complexity: some new twists.
abstract: The current knowledge on topological knots in protein structure is reviewed, considering in turn, knots with three, four and five strand crossings. The latter is the most recent to be identified and has two distinct topological forms. The knot observed in the protein structure is the form that requires the least number of strand crossings to become un-knotted. The position of the chain termini must also correspond to a position that allows (un) knotting in one move. This is postulated as a general property of protein knots and other more complex knots with this property are proposed as the next most likely knots that might be found in a protein. It is also noted that the "Jelly-roll" fold found in some all-beta proteins would provide likely candidates. Alternative measures of knottedness and entanglement are reviewed, including the occurrence of slip-knots. These measures are related to the complexity of the protein fold and may provide useful filters for selecting predicted model structures.
authors.affiliation: Division of Mathematical Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK. wtaylor@nimr.mrc.ac.uk
authors.forename: William R
authors.initials: WR
authors.lastname: Taylor
mesh_terms: D019878:Carboxyl and Carbamoyl Transferases / Q000737:chemistry; D004798:Enzymes / Q000737:chemistry; D050540:Ketol-Acid Reductoisomerase / Q000737:chemistry; D008716:Methionine Adenosyltransferase / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D012359:tRNA Methyltransferases / Q000737:chemistry
chemical_list: D004798:Enzymes; D011506:Proteins; D050540:Ketol-Acid Reductoisomerase; D012359:tRNA Methyltransferases; D019878:Carboxyl and Carbamoyl Transferases; C021580:Methylmalonyl-CoA carboxytransferase; D008716:Methionine Adenosyltransferase