It is possible to group records into categories based upon how often the record type appears in an entry.
Single
There are records which may only appear one time (without continuations) in a file. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION
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CRYST1 Unit cell parameters, space group, and Z.
END Last record in the file.
HEADER First line of the entry, contains PDB ID code,
classification, and date of deposition.
MASTER Control record for bookkeeping.
ORIGXn Transformation from orthogonal coordinates to the submitted
coordinates (n = 1, 2, or 3).
SCALEn Transformation from orthogonal coordinates to fractional
crystallographic coordinates (n = 1, 2, or 3).
It is an error for a duplicate of any of these records to appear in an entry.
Single Continued
There are records that conceptually exist only once in an entry, but the information content may exceed the number of columns available. These records are therefore continued on subsequent lines. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION
-------------------------------------------------------------------------------
AUTHOR List of contributors.
CAVEAT Severe error indicator. Entries with this record must be
used with care.
COMPND Description of macromolecular contents of the entry.
EXPDTA Experimental technique used for the structure determination.
KEYWDS List of keywords describing the macromolecule.
OBSLTE Statement that the entry has been removed from distribution
and list of the ID code(s) which replaced it.
SOURCE Biological source of macromolecules in the entry.
SPRSDE List of entries withdrawn from release and replaced by
current entry.
TITLE Description of the experiment represented in the entry.
The second and subsequent lines contain a continuation field which is a right-justified integer. This number increments by one for each additional line of the record, and is followed by a blank character.
Multiple
Most record types appear multiple times, often in groups where the information is not logically concatenated but is presented in the form of a list. Many of these record types have a custom serialization that may be used not only to order the records, but also to connect to other record types. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION
--------------------------------------------------------------------------------
ANISOU Anisotropic temperature factors.
ATOM Atomic coordinate records for standard groups.
CISPEP Identification of peptide residues in cis conformation.
CONECT Connectivity records.
DBREF Reference to the entry in the sequence database(s).
HELIX Identification of helical substructures.
HET Identification of non-standard groups or residues (heterogens)
HETSYN Synonymous compound names for heterogens.
HYDBND Identification of hydrogen bonds.
LINK Identification of inter-residue bonds.
MODRES Identification of modifications to standard residues.
MTRIXn Transformations expressing non-crystallographic symmetry
(n = 1, 2, or 3). There may be multiple sets of these records.
REVDAT Revision date and related information.
SEQADV Identification of conflicts between PDB and the named sequence
database.
SEQRES Primary sequence of backbone residues.
SHEET Identification of sheet substructures.
SIGATM Standard deviations of atomic parameters.
SIGUIJ Standard deviations of anisotropic temperature factors.
SITE Identification of groups comprising important sites.
SLTBRG Identification of salt bridges
SSBOND Identification of disulfide bonds.
TURN Identification of turns.
TVECT Translation vector for infinite covalently connected
structures.
Multiple Continued
There are records that conceptually exist multiple times in an entry, but the information content may exceed the number of columns available. These records are therefore continued on subsequent lines. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION ------------------------------------------------------------------------------- FORMUL Chemical formula of non-standard groups. HETATM Atomic coordinate records for heterogens. HETNAM Compound name of the heterogens.
The second and subsequent lines contain a continuation field which is a right-justified integer. This number increments by one for each additional line of the record, and is followed by a blank character.
Grouping
There are three record types used to group other records. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION
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ENDMDL End-of-model record for multiple structures in a single
coordinate entry.
MODEL Specification of model number for multiple structures in a
single coordinate entry.
TER Chain terminator.
The MODEL/ENDMDL records surround groups of ATOM, HETATM, SIGATM, ANISOU, SIGUIJ, and TER records. TER records indicate the end of a chain.
Other
The remaining record types have a detailed inner structure. Listed alphabetically, these are:
RECORD TYPE DESCRIPTION ------------------------------------------------------------------------------ JRNL Literature citation that defines the coordinate set. REMARK General remarks, some are structured and some are free form.