Overview
The LINK records specify connectivity between residues that is not implied by the primary structure. Connectivity is expressed in terms of the atom names. This record supplements information given in CONECT records and is provided here for convenience in searching.
Record Format
COLUMNS DATA TYPE FIELD DEFINITION -------------------------------------------------------------------------------- 1 - 6 Record name "LINK " 13 - 16 Atom name1 Atom name. 17 Character altLoc1 Alternate location indicator. 18 - 20 Residue name resName1 Residue name. 22 Character chainID1 Chain identifier. 23 - 26 Integer resSeq1 Residue sequence number. 27 AChar iCode1 Insertion code. 43 - 46 Atom name2 Atom name. 47 Character altLoc2 Alternate location indicator. 48 - 50 Residue name resName2 Residue name. 52 Character chainID2 Chain identifier. 53 - 56 Integer resSeq2 Residue sequence number. 57 AChar iCode2 Insertion code. 60 - 65 SymOP sym1 Symmetry operator for 1st atom. 67 - 72 SymOP sym2 Symmetry operator for 2nd atom.
Details
* The atoms involved in bonds between HET groups or between a HET group and standard residue are listed.
* Interresidue linkages not implied by the primary structure are listed (e.g., reduced peptide bond).
* Non-standard linkages between residues, e.g., side-chain to side-chain, are listed.
* Each LINK record specifies one linkage.
* These records do not specify connectivity within a HET group (see CONECT), hydrogen bonds (see HYDBND), or disulfide bridges (see SSBOND).
* Hydrogen bonds and salt bridges are described on HYDBND and SLTBRG records, respectively.
* sym1 and sym2 are given as blank when the identity operator (and no cell translation) is to be applied to the atom.
* For NMR entries only one set (or model) of LINK records will be supplied.
Verification/Validation/Value Authority Control
The distance between the pair of atoms listed must be consistent with the bonding.
Relationships to Other Record Types
CONECT records are generated from LINKs when both atoms are present in the entry. If symmetry operators are given to generate one of the residues involved in the bond, REMARK 290 defines the symmetry transformation.
Example
1 2 3 4 5 6 7
123456789012345678901234567890123456789012345678901234567890123456789012
LINK O1 DDA 1 C3 DDL 2
LINK MN MN 391 OE2 GLU 217 2565