Overview
SHEET records are used to identify the position of sheets in the molecule. Sheets are both named and numbered. The residues where the sheet begins and ends are noted.
Record Format
COLUMNS DATA TYPE FIELD DEFINITION
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1 - 6 Record name "SHEET "
8 - 10 Integer strand Strand number which starts at 1 for
each strand within a sheet and
increases by one.
12 - 14 LString(3) sheetID Sheet identifier.
15 - 16 Integer numStrands Number of strands in sheet.
18 - 20 Residue name initResName Residue name of initial residue.
22 Character initChainID Chain identifier of initial residue
in strand.
23 - 26 Integer initSeqNum Sequence number of initial residue
in strand.
27 AChar initICode Insertion code of initial residue
in strand.
29 - 31 Residue name endResName Residue name of terminal residue.
33 Character endChainID Chain identifier of terminal
residue.
34 - 37 Integer endSeqNum Sequence number of terminal residue.
38 AChar endICode Insertion code of terminal residue.
39 - 40 Integer sense Sense of strand with respect to
previous strand in the sheet. 0
if first strand, 1 if parallel,
-1 if anti-parallel.
42 - 45 Atom curAtom Registration. Atom name in current
strand.
46 - 48 Residue name curResName Registration. Residue name in
current strand.
50 Character curChainId Registration. Chain identifier in
current strand.
51 - 54 Integer curResSeq Registration. Residue sequence
number in current strand.
55 AChar curICode Registration. Insertion code in
current strand.
57 - 60 Atom prevAtom Registration. Atom name in
previous strand.
61 - 63 Residue name prevResName Registration. Residue name in
previous strand.
65 Character prevChainId Registration. Chain identifier in
previous strand.
66 - 69 Integer prevResSeq Registration. Residue sequence
number in previous strand.
70 AChar prevICode Registration. Insertion code in
previous strand.
Details
* The initial residue for a strand is its N-terminus. Strand registration information is provided in columns 39 - 70. Strands are listed starting with one edge of the sheet and continuing to the spatially adjacent strand.
* The sense in columns 39 - 40 indicates whether strand n is parallel (sense = 1) or anti-parallel (sense = -1) to strand n-1. Sense is equal to zero (0) for the first strand of a sheet.
* The registration (columns 42 - 70) of strand n to strand n-1 may be specified by one hydrogen bond between each such pair of strands. This is done by providing the hydrogen bonding between the current and previous strands. No registration information should be provided for the first strand.
* For structures which form a closed sheet (beta-barrel), the first strand is repeated as the last strand. An explanatory remark is included in the REMARK section.
* Split strands, or strands with two or more runs of residues from discontinuous parts of the amino acid sequence, are explicitly listed. Provide a description to be included in the REMARK section.
Verification/Validation/Value Authority Control
SHEET records are now being generated automatically by PDB using the Kabsch and Sander algorithm [Kabsch and Sander, Biopolymers 22: 2577-2637 (1983)], although they may be provided by the depositor instead. PDB verifies that named residues exist in the ATOM records.
Relationships to Other Record Types
If the entry contains bifurcated sheets or beta-barrels, the relevant REMARK records must be provided. See the REMARK section for details.
Example
1 2 3 4 5 6 7
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SHEET 1 A 5 THR A 107 ARG A 110 0
SHEET 2 A 5 ILE A 96 THR A 99 -1 N LYS A 98 O THR A 107
SHEET 3 A 5 ARG A 87 SER A 91 -1 N LEU A 89 O TYR A 97
SHEET 4 A 5 TRP A 71 ASP A 75 -1 N ALA A 74 O ILE A 88
SHEET 5 A 5 GLY A 52 PHE A 56 -1 N PHE A 56 O TRP A 71
SHEET 1 B 5 THR B 107 ARG B 110 0
SHEET 2 B 5 ILE B 96 THR B 99 -1 N LYS B 98 O THR B 107
SHEET 3 B 5 ARG B 87 SER B 91 -1 N LEU B 89 O TYR B 97
SHEET 4 B 5 TRP B 71 ASP B 75 -1 N ALA B 74 O ILE B 88
SHEET 5 B 5 GLY B 52 ILE B 55 -1 N ASP B 54 O GLU B 73
The sheet presented as BS1 below is an eight-stranded beta-barrel. This is represented by a nine-stranded sheet in which the first and last strands are identical.
SHEET 1 BS1 9 VAL 13 ILE 17 0 SHEET 2 BS1 9 ALA 70 ILE 73 1 O TRP 72 N ILE 17 SHEET 3 BS1 9 LYS 127 PHE 132 1 O ILE 129 N ILE 73 SHEET 4 BS1 9 GLY 221 ASP 225 1 O GLY 221 N ILE 130 SHEET 5 BS1 9 VAL 248 GLU 253 1 O PHE 249 N ILE 222 SHEET 6 BS1 9 LEU 276 ASP 278 1 N LEU 277 O GLY 252 SHEET 7 BS1 9 TYR 310 THR 318 1 O VAL 317 N ASP 278 SHEET 8 BS1 9 VAL 351 TYR 356 1 O VAL 351 N THR 318 SHEET 9 BS1 9 VAL 13 ILE 17 1 N VAL 14 O PRO 352
The sheet structure of this example is bifurcated. In order to represent this feature, two sheets are defined. Strands 2 and 3 of BS7 and BS8 are identical.
SHEET 1 BS7 3 HIS 662 THR 665 0 SHEET 2 BS7 3 LYS 639 LYS 648 -1 N PHE 643 O HIS 662 SHEET 3 BS7 3 ASN 596 VAL 600 -1 N TYR 598 O ILE 646 SHEET 1 BS8 3 ASN 653 TRP 656 0 SHEET 2 BS8 3 LYS 639 LYS 648 -1 N LYS 647 O THR 655 SHEET 3 BS8 3 ASN 596 VAL 600 -1 N TYR 598 O ILE 646