UniProtKB - Q9HCE7 (SMUF1_HUMAN)
E3 ubiquitin-protein ligase SMURF1
SMURF1
Functioni
Catalytic activityi
- S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine.1 Publication EC:2.3.2.26
: protein ubiquitination Pathwayi
This protein is involved in the pathway protein ubiquitination, which is part of Protein modification.View all proteins of this organism that are known to be involved in the pathway protein ubiquitination and in Protein modification.
Sites
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Active sitei | 725 | Glycyl thioester intermediate | 1 |
GO - Molecular functioni
- activin binding Source: BHF-UCL
- I-SMAD binding Source: BHF-UCL
- phospholipid binding Source: ParkinsonsUK-UCL
- R-SMAD binding Source: BHF-UCL
- ubiquitin protein ligase activity Source: BHF-UCL
- ubiquitin-protein transferase activity Source: UniProtKB
GO - Biological processi
- BMP signaling pathway Source: UniProtKB
- cell differentiation Source: UniProtKB
- ectoderm development Source: UniProtKB
- engulfment of target by autophagosome Source: ParkinsonsUK-UCL
- negative regulation of BMP signaling pathway Source: BHF-UCL
- negative regulation of ossification Source: Ensembl
- negative regulation of transforming growth factor beta receptor signaling pathway Source: BHF-UCL
- parkin-mediated stimulation of mitophagy in response to mitochondrial depolarization Source: Ensembl
- positive regulation of dendrite extension Source: UniProtKB
- positive regulation of protein catabolic process Source: GO_Central
- positive regulation of ubiquitin-dependent protein catabolic process Source: CACAO
- proteasome-mediated ubiquitin-dependent protein catabolic process Source: BHF-UCL
- protein export from nucleus Source: BHF-UCL
- protein localization to cell surface Source: BHF-UCL
- protein localization to plasma membrane Source: ParkinsonsUK-UCL
- protein polyubiquitination Source: UniProtKB
- protein targeting to vacuole involved in autophagy Source: ParkinsonsUK-UCL
- protein ubiquitination Source: BHF-UCL
- receptor catabolic process Source: BHF-UCL
- substrate localization to autophagosome Source: ParkinsonsUK-UCL
- transforming growth factor beta receptor signaling pathway Source: Reactome
- ubiquitin-dependent protein catabolic process Source: UniProtKB
- ubiquitin-dependent SMAD protein catabolic process Source: BHF-UCL
- Wnt signaling pathway, planar cell polarity pathway Source: Reactome
Keywordsi
Molecular function | Transferase |
Biological process | Differentiation, Ubl conjugation pathway |
Enzyme and pathway databases
BRENDAi | 2.3.2.B9 2681 6.3.2.19 2681 |
Reactomei | R-HSA-201451 Signaling by BMP R-HSA-2173788 Downregulation of TGF-beta receptor signaling R-HSA-2173791 TGF-beta receptor signaling in EMT (epithelial to mesenchymal transition) R-HSA-4608870 Asymmetric localization of PCP proteins R-HSA-5632684 Hedgehog 'on' state R-HSA-8939902 Regulation of RUNX2 expression and activity R-HSA-8941858 Regulation of RUNX3 expression and activity R-HSA-983168 Antigen processing: Ubiquitination & Proteasome degradation |
SignaLinki | Q9HCE7 |
SIGNORi | Q9HCE7 |
UniPathwayi | UPA00143 |
Names & Taxonomyi
Protein namesi | Recommended name: E3 ubiquitin-protein ligase SMURF1 (EC:2.3.2.261 Publication)Short name: hSMURF1 Alternative name(s): HECT-type E3 ubiquitin transferase SMURF1 SMAD ubiquitination regulatory factor 1 SMAD-specific E3 ubiquitin-protein ligase 1 |
Gene namesi | Name:SMURF1 Synonyms:KIAA1625 |
Organismi | Homo sapiens (Human) |
Taxonomic identifieri | 9606 [NCBI] |
Taxonomic lineagei | Eukaryota › Metazoa › Chordata › Craniata › Vertebrata › Euteleostomi › Mammalia › Eutheria › Euarchontoglires › Primates › Haplorrhini › Catarrhini › Hominidae › Homo |
Proteomesi |
|
Organism-specific databases
HGNCi | HGNC:16807 SMURF1 |
MIMi | 605568 gene |
neXtProti | NX_Q9HCE7 |
Subcellular locationi
Plasma membrane
- Cell membrane 1 Publication; Peripheral membrane protein 1 Publication; Cytoplasmic side 1 Publication
Other locations
- Cytoplasm 1 Publication
Cytosol
- cytosol Source: Reactome
Extracellular region or secreted
- extracellular exosome Source: UniProtKB
Nucleus
- nucleoplasm Source: Reactome
Plasma Membrane
- plasma membrane Source: BHF-UCL
Other locations
- axon Source: Ensembl
- cell Source: GOC
- cytoplasm Source: UniProtKB
- neuronal cell body Source: Ensembl
Keywords - Cellular componenti
Cell membrane, Cytoplasm, MembranePathology & Biotechi
Mutagenesis
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Mutagenesisi | 28 | K → A: Fails to ubiquitinate RHOA; when associated with A-85. 1 Publication | 1 | |
Mutagenesisi | 85 | K → A: Fails to ubiquitinate RHOA; when associated with A-28. 1 Publication | 1 | |
Mutagenesisi | 350 | K → R: Abolishes FBXL15-mediated ubiquitination and degradation; when associated with R-381 and R-381. 1 Publication | 1 | |
Mutagenesisi | 381 | K → R: Abolishes FBXL15-mediated ubiquitination and degradation; when associated with R-350 and R-383. Abolishes FBXL15-mediated ubiquitination and degradation; when associated with R-383. 1 Publication | 1 | |
Mutagenesisi | 383 | K → R: Abolishes FBXL15-mediated ubiquitination and degradation; when associated with R-350 and R-381. Abolishes FBXL15-mediated ubiquitination and degradation; when associated with R-381. 1 Publication | 1 | |
Mutagenesisi | 725 | C → A: Loss of enzyme activity, without abolishing FBXL15-mediated ubiquitination. 2 Publications | 1 |
Organism-specific databases
DisGeNETi | 57154 |
OpenTargetsi | ENSG00000198742 |
PharmGKBi | PA134987175 |
Miscellaneous databases
Pharosi | Q9HCE7 |
Chemistry databases
ChEMBLi | CHEMBL3879859 |
Polymorphism and mutation databases
BioMutai | SMURF1 |
DMDMi | 17865625 |
PTM / Processingi
Molecule processing
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
ChainiPRO_0000120326 | 1 – 757 | E3 ubiquitin-protein ligase SMURF1Add BLAST | 757 |
Amino acid modifications
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Modified residuei | 200 | PhosphoserineCombined sources | 1 | |
Cross-linki | 381 | Glycyl lysine isopeptide (Lys-Gly) (interchain with G-Cter in ubiquitin)1 Publication | ||
Cross-linki | 383 | Glycyl lysine isopeptide (Lys-Gly) (interchain with G-Cter in ubiquitin)1 Publication |
Post-translational modificationi
Keywords - PTMi
Isopeptide bond, Phosphoprotein, Ubl conjugationProteomic databases
EPDi | Q9HCE7 |
jPOSTi | Q9HCE7 |
MassIVEi | Q9HCE7 |
MaxQBi | Q9HCE7 |
PaxDbi | Q9HCE7 |
PeptideAtlasi | Q9HCE7 |
PRIDEi | Q9HCE7 |
ProteomicsDBi | 81693 [Q9HCE7-1] 81694 [Q9HCE7-2] |
PTM databases
iPTMneti | Q9HCE7 |
PhosphoSitePlusi | Q9HCE7 |
Expressioni
Tissue specificityi
Gene expression databases
Bgeei | ENSG00000198742 Expressed in 201 organ(s), highest expression level in testis |
Genevisiblei | Q9HCE7 HS |
Organism-specific databases
HPAi | HPA055245 |
Interactioni
Subunit structurei
Interacts with TRAF4.
Interacts (via HECT domain) with FBXL15 (via LRR repeats).
Interacts with SMAD7 and TGFBR1; SMAD7 recruits SMURF1 to TGFBR1 and regulates TGF-beta receptor degradation.
Interacts with MAVS; the interaction is mediated by NDFIP1 (PubMed:23087404).
5 PublicationsBinary interactionsi
GO - Molecular functioni
- I-SMAD binding Source: BHF-UCL
- R-SMAD binding Source: BHF-UCL
Protein-protein interaction databases
BioGridi | 121411, 427 interactors |
CORUMi | Q9HCE7 |
DIPi | DIP-36709N |
IntActi | Q9HCE7, 29 interactors |
MINTi | Q9HCE7 |
STRINGi | 9606.ENSP00000354621 |
Chemistry databases
BindingDBi | Q9HCE7 |
Structurei
Secondary structure
3D structure databases
SMRi | Q9HCE7 |
ModBasei | Search... |
PDBe-KBi | Search... |
Miscellaneous databases
EvolutionaryTracei | Q9HCE7 |
Family & Domainsi
Domains and Repeats
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Domaini | 1 – 99 | C2PROSITE-ProRule annotationAdd BLAST | 99 | |
Domaini | 234 – 267 | WW 1PROSITE-ProRule annotationAdd BLAST | 34 | |
Domaini | 306 – 339 | WW 2PROSITE-ProRule annotationAdd BLAST | 34 | |
Domaini | 420 – 757 | HECTPROSITE-ProRule annotationAdd BLAST | 338 |
Domaini
Keywords - Domaini
RepeatPhylogenomic databases
eggNOGi | KOG0940 Eukaryota COG5021 LUCA |
GeneTreei | ENSGT00940000158690 |
HOGENOMi | HOG000208451 |
InParanoidi | Q9HCE7 |
KOi | K04678 |
OMAi | CKLNPTD |
OrthoDBi | 167687at2759 |
PhylomeDBi | Q9HCE7 |
TreeFami | TF323658 |
Family and domain databases
CDDi | cd00078 HECTc, 1 hit cd00201 WW, 2 hits |
Gene3Di | 2.60.40.150, 1 hit |
InterProi | View protein in InterPro IPR000008 C2_dom IPR035892 C2_domain_sf IPR024928 E3_ub_ligase_SMURF1 IPR000569 HECT_dom IPR035983 Hect_E3_ubiquitin_ligase IPR001202 WW_dom IPR036020 WW_dom_sf |
Pfami | View protein in Pfam PF00168 C2, 1 hit PF00632 HECT, 1 hit PF00397 WW, 2 hits |
PIRSFi | PIRSF001569 E3_ub_ligase_SMURF1, 1 hit |
SMARTi | View protein in SMART SM00239 C2, 1 hit SM00119 HECTc, 1 hit SM00456 WW, 2 hits |
SUPFAMi | SSF51045 SSF51045, 2 hits SSF56204 SSF56204, 1 hit |
PROSITEi | View protein in PROSITE PS50004 C2, 1 hit PS50237 HECT, 1 hit PS01159 WW_DOMAIN_1, 1 hit PS50020 WW_DOMAIN_2, 2 hits |
s (2)i Sequence
Sequence statusi: Complete.
This entry describes 2 produced by isoformsialternative splicing. AlignAdd to basketThis isoform has been chosen as the sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry. canonicali
10 20 30 40 50
MSNPGTRRNG SSIKIRLTVL CAKNLAKKDF FRLPDPFAKI VVDGSGQCHS
60 70 80 90 100
TDTVKNTLDP KWNQHYDLYV GKTDSITISV WNHKKIHKKQ GAGFLGCVRL
110 120 130 140 150
LSNAISRLKD TGYQRLDLCK LNPSDTDAVR GQIVVSLQTR DRIGTGGSVV
160 170 180 190 200
DCRGLLENEG TVYEDSGPGR PLSCFMEEPA PYTDSTGAAA GGGNCRFVES
210 220 230 240 250
PSQDQRLQAQ RLRNPDVRGS LQTPQNRPHG HQSPELPEGY EQRTTVQGQV
260 270 280 290 300
YFLHTQTGVS TWHDPRIPSP SGTIPGGDAA FLYEFLLQGH TSEPRDLNSV
310 320 330 340 350
NCDELGPLPP GWEVRSTVSG RIYFVDHNNR TTQFTDPRLH HIMNHQCQLK
360 370 380 390 400
EPSQPLPLPS EGSLEDEELP AQRYERDLVQ KLKVLRHELS LQQPQAGHCR
410 420 430 440 450
IEVSREEIFE ESYRQIMKMR PKDLKKRLMV KFRGEEGLDY GGVAREWLYL
460 470 480 490 500
LCHEMLNPYY GLFQYSTDNI YMLQINPDSS INPDHLSYFH FVGRIMGLAV
510 520 530 540 550
FHGHYINGGF TVPFYKQLLG KPIQLSDLES VDPELHKSLV WILENDITPV
560 570 580 590 600
LDHTFCVEHN AFGRILQHEL KPNGRNVPVT EENKKEYVRL YVNWRFMRGI
610 620 630 640 650
EAQFLALQKG FNELIPQHLL KPFDQKELEL IIGGLDKIDL NDWKSNTRLK
660 670 680 690 700
HCVADSNIVR WFWQAVETFD EERRARLLQF VTGSTRVPLQ GFKALQGSTG
710 720 730 740 750
AAGPRLFTIH LIDANTDNLP KAHTCFNRID IPPYESYEKL YEKLLTAVEE
TCGFAVE
The sequence of this isoform differs from the canonical sequence as follows:
269-294: Missing.
Sequence cautioni
Experimental Info
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Sequence conflicti | 447 | W → G in AAI44415 (PubMed:15489334).Curated | 1 | |
Sequence conflicti | 697 – 699 | Missing in AAI36805 (PubMed:15489334).Curated | 3 | |
Sequence conflicti | 697 – 699 | Missing in AAI44415 (PubMed:15489334).Curated | 3 |
Natural variant
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Natural variantiVAR_052959 | 466 | S → Y. Corresponds to variant dbSNP:rs13246077Ensembl. | 1 |
Alternative sequence
Feature key | Position(s) | DescriptionActions | Graphical view | Length |
---|---|---|---|---|
Alternative sequenceiVSP_006812 | 269 – 294 | Missing in isoform Short. 2 PublicationsAdd BLAST | 26 |
Sequence databases
Select the link destinations: EMBLi GenBanki DDBJi Links Updated | AB046845 mRNA Translation: BAB13451.1 Different initiation. AC004893 Genomic DNA Translation: AAC62434.1 AF464850 mRNA Translation: AAM90910.1 AC073468 Genomic DNA No translation available. AC114500 Genomic DNA No translation available. CH236956 Genomic DNA Translation: EAL23885.1 CH236956 Genomic DNA Translation: EAL23886.1 CH471091 Genomic DNA Translation: EAW76687.1 CH471091 Genomic DNA Translation: EAW76688.1 BC136804 mRNA Translation: AAI36805.1 BC144414 mRNA Translation: AAI44415.1 BC152468 mRNA Translation: AAI52469.1 AF199364 mRNA Translation: AAF08298.2 |
CCDSi | CCDS34689.1 [Q9HCE7-2] CCDS34690.1 [Q9HCE7-1] |
RefSeqi | NP_001186776.1, NM_001199847.1 NP_065162.1, NM_020429.2 [Q9HCE7-1] NP_851994.1, NM_181349.2 [Q9HCE7-2] |
Genome annotation databases
Ensembli | ENST00000361125; ENSP00000354621; ENSG00000198742 [Q9HCE7-1] ENST00000361368; ENSP00000355326; ENSG00000198742 [Q9HCE7-2] ENST00000638461; ENSP00000491036; ENSG00000284126 [Q9HCE7-2] ENST00000638647; ENSP00000492201; ENSG00000284126 [Q9HCE7-1] |
GeneIDi | 57154 |
KEGGi | hsa:57154 |
UCSCi | uc003upu.3 human [Q9HCE7-1] |
Keywords - Coding sequence diversityi
Alternative splicing, PolymorphismSimilar proteinsi
Cross-referencesi
Sequence databases
Select the link destinations: EMBLi GenBanki DDBJi Links Updated | AB046845 mRNA Translation: BAB13451.1 Different initiation. AC004893 Genomic DNA Translation: AAC62434.1 AF464850 mRNA Translation: AAM90910.1 AC073468 Genomic DNA No translation available. AC114500 Genomic DNA No translation available. CH236956 Genomic DNA Translation: EAL23885.1 CH236956 Genomic DNA Translation: EAL23886.1 CH471091 Genomic DNA Translation: EAW76687.1 CH471091 Genomic DNA Translation: EAW76688.1 BC136804 mRNA Translation: AAI36805.1 BC144414 mRNA Translation: AAI44415.1 BC152468 mRNA Translation: AAI52469.1 AF199364 mRNA Translation: AAF08298.2 |
CCDSi | CCDS34689.1 [Q9HCE7-2] CCDS34690.1 [Q9HCE7-1] |
RefSeqi | NP_001186776.1, NM_001199847.1 NP_065162.1, NM_020429.2 [Q9HCE7-1] NP_851994.1, NM_181349.2 [Q9HCE7-2] |
3D structure databases
Select the link destinations: PDBei RCSB PDBi PDBji Links Updated | PDB entry | Method | Resolution (Å) | Chain | Positions | PDBsum |
2LAZ | NMR | - | A | 235-267 | [»] | |
2LB0 | NMR | - | A | 235-267 | [»] | |
2LB1 | NMR | - | A | 305-340 | [»] | |
2LTX | NMR | - | A | 306-340 | [»] | |
3PYC | X-ray | 1.96 | A | 13-140 | [»] | |
SMRi | Q9HCE7 | |||||
ModBasei | Search... | |||||
PDBe-KBi | Search... |
Protein-protein interaction databases
BioGridi | 121411, 427 interactors |
CORUMi | Q9HCE7 |
DIPi | DIP-36709N |
IntActi | Q9HCE7, 29 interactors |
MINTi | Q9HCE7 |
STRINGi | 9606.ENSP00000354621 |
Chemistry databases
BindingDBi | Q9HCE7 |
ChEMBLi | CHEMBL3879859 |
PTM databases
iPTMneti | Q9HCE7 |
PhosphoSitePlusi | Q9HCE7 |
Polymorphism and mutation databases
BioMutai | SMURF1 |
DMDMi | 17865625 |
Proteomic databases
EPDi | Q9HCE7 |
jPOSTi | Q9HCE7 |
MassIVEi | Q9HCE7 |
MaxQBi | Q9HCE7 |
PaxDbi | Q9HCE7 |
PeptideAtlasi | Q9HCE7 |
PRIDEi | Q9HCE7 |
ProteomicsDBi | 81693 [Q9HCE7-1] 81694 [Q9HCE7-2] |
Protocols and materials databases
ABCDi | Q9HCE7 |
Genome annotation databases
Ensembli | ENST00000361125; ENSP00000354621; ENSG00000198742 [Q9HCE7-1] ENST00000361368; ENSP00000355326; ENSG00000198742 [Q9HCE7-2] ENST00000638461; ENSP00000491036; ENSG00000284126 [Q9HCE7-2] ENST00000638647; ENSP00000492201; ENSG00000284126 [Q9HCE7-1] |
GeneIDi | 57154 |
KEGGi | hsa:57154 |
UCSCi | uc003upu.3 human [Q9HCE7-1] |
Organism-specific databases
CTDi | 57154 |
DisGeNETi | 57154 |
GeneCardsi | SMURF1 |
HGNCi | HGNC:16807 SMURF1 |
HPAi | HPA055245 |
MIMi | 605568 gene |
neXtProti | NX_Q9HCE7 |
OpenTargetsi | ENSG00000198742 |
PharmGKBi | PA134987175 |
HUGEi | Search... |
GenAtlasi | Search... |
Phylogenomic databases
eggNOGi | KOG0940 Eukaryota COG5021 LUCA |
GeneTreei | ENSGT00940000158690 |
HOGENOMi | HOG000208451 |
InParanoidi | Q9HCE7 |
KOi | K04678 |
OMAi | CKLNPTD |
OrthoDBi | 167687at2759 |
PhylomeDBi | Q9HCE7 |
TreeFami | TF323658 |
Enzyme and pathway databases
UniPathwayi | UPA00143 |
BRENDAi | 2.3.2.B9 2681 6.3.2.19 2681 |
Reactomei | R-HSA-201451 Signaling by BMP R-HSA-2173788 Downregulation of TGF-beta receptor signaling R-HSA-2173791 TGF-beta receptor signaling in EMT (epithelial to mesenchymal transition) R-HSA-4608870 Asymmetric localization of PCP proteins R-HSA-5632684 Hedgehog 'on' state R-HSA-8939902 Regulation of RUNX2 expression and activity R-HSA-8941858 Regulation of RUNX3 expression and activity R-HSA-983168 Antigen processing: Ubiquitination & Proteasome degradation |
SignaLinki | Q9HCE7 |
SIGNORi | Q9HCE7 |
Miscellaneous databases
ChiTaRSi | SMURF1 human |
EvolutionaryTracei | Q9HCE7 |
GeneWikii | SMURF1 |
GenomeRNAii | 57154 |
Pharosi | Q9HCE7 |
PROi | PR:Q9HCE7 |
SOURCEi | Search... |
Gene expression databases
Bgeei | ENSG00000198742 Expressed in 201 organ(s), highest expression level in testis |
Genevisiblei | Q9HCE7 HS |
Family and domain databases
CDDi | cd00078 HECTc, 1 hit cd00201 WW, 2 hits |
Gene3Di | 2.60.40.150, 1 hit |
InterProi | View protein in InterPro IPR000008 C2_dom IPR035892 C2_domain_sf IPR024928 E3_ub_ligase_SMURF1 IPR000569 HECT_dom IPR035983 Hect_E3_ubiquitin_ligase IPR001202 WW_dom IPR036020 WW_dom_sf |
Pfami | View protein in Pfam PF00168 C2, 1 hit PF00632 HECT, 1 hit PF00397 WW, 2 hits |
PIRSFi | PIRSF001569 E3_ub_ligase_SMURF1, 1 hit |
SMARTi | View protein in SMART SM00239 C2, 1 hit SM00119 HECTc, 1 hit SM00456 WW, 2 hits |
SUPFAMi | SSF51045 SSF51045, 2 hits SSF56204 SSF56204, 1 hit |
PROSITEi | View protein in PROSITE PS50004 C2, 1 hit PS50237 HECT, 1 hit PS01159 WW_DOMAIN_1, 1 hit PS50020 WW_DOMAIN_2, 2 hits |
ProtoNeti | Search... |
MobiDBi | Search... |
Entry informationi
Entry namei | SMUF1_HUMAN | |
Accessioni | Q9HCE7Primary (citable) accession number: Q9HCE7 Secondary accession number(s): A4D279 Q9UJT8 | |
Entry historyi | Integrated into UniProtKB/Swiss-Prot: | December 13, 2001 |
Last sequence update: | December 13, 2001 | |
Last modified: | November 13, 2019 | |
This is version 187 of the entry and version 2 of the sequence. See complete history. | ||
Entry statusi | Reviewed (UniProtKB/Swiss-Prot) | |
Annotation program | Chordata Protein Annotation Program | |
Disclaimer | Any medical or genetic information present in this entry is provided for research, educational and informational purposes only. It is not in any way intended to be used as a substitute for professional medical advice, diagnosis, treatment or care. |
Miscellaneousi
Keywords - Technical termi
3D-structure, Complete proteome, Reference proteomeDocuments
- Human chromosome 7
Human chromosome 7: entries, gene names and cross-references to MIM - Human entries with polymorphisms or disease mutations
List of human entries with polymorphisms or disease mutations - Human polymorphisms and disease mutations
Index of human polymorphisms and disease mutations - MIM cross-references
Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot - PATHWAY comments
Index of metabolic and biosynthesis pathways - PDB cross-references
Index of Protein Data Bank (PDB) cross-references