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Ras-related C3 botulinum toxin substrate 1



Homo sapiens (Human)
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli


Plasma membrane-associated small GTPase which cycles between active GTP-bound and inactive GDP-bound states. In its active state, binds to a variety of effector proteins to regulate cellular responses such as secretory processes, phagocytosis of apoptotic cells, epithelial cell polarization and growth-factor induced formation of membrane ruffles. Rac1 p21/rho GDI heterodimer is the active component of the cytosolic factor sigma 1, which is involved in stimulation of the NADPH oxidase activity in macrophages. Essential for the SPATA13-mediated regulation of cell migration and adhesion assembly and disassembly. Stimulates PKN2 kinase activity. In concert with RAB7A, plays a role in regulating the formation of RBs (ruffled borders) in osteoclasts. In glioma cells, promotes cell migration and invasion. In podocytes, promotes nuclear shuttling of NR3C2; this modulation is required for a proper kidney functioning. Required for atypical chemokine receptor ACKR2-induced LIMK1-PAK1-dependent phosphorylation of cofilin (CFL1) and for up-regulation of ACKR2 from endosomal compartment to cell membrane, increasing its efficiency in chemokine uptake and degradation. In synapses, seems to mediate the regulation of F-actin cluster formation performed by SHANK3.
Isoform B has an accelerated GEF-independent GDP/GTP exchange and an impaired GTP hydrolysis, which is restored partially by GTPase-activating proteins. It is able to bind to the GTPase-binding domain of PAK but not full-length PAK in a GTP-dependent manner, suggesting that the insertion does not completely abolish effector interaction.

Enzyme regulationi

Regulated by guanine nucleotide exchange factors (GEFs) which promote the exchange of bound GDP for free GTP, GTPase activating proteins (GAPs) which increase the GTP hydrolysis activity, and GDP dissociation inhibitors which inhibit the dissociation of the nucleotide from the GTPase. GTP hydrolysis is stimulated by ARHGAP30.1 Publication


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Nucleotide bindingi10 – 17GTPBy similarity8
Nucleotide bindingi57 – 61GTPBy similarity5
Nucleotide bindingi115 – 118GTPBy similarity4

GO - Molecular functioni

  • ATPase binding Source: Ensembl
  • enzyme binding Source: BHF-UCL
  • GTPase activity Source: UniProtKB
  • GTP binding Source: UniProtKB
  • histone deacetylase binding Source: Ensembl
  • protein kinase binding Source: CAFA
  • Rab GTPase binding Source: Ensembl
  • Rho GDP-dissociation inhibitor binding Source: UniProtKB
  • thioesterase binding Source: UniProtKB

GO - Biological processi

  • actin cytoskeleton organization Source: MGI
  • actin filament polymerization Source: UniProtKB
  • anatomical structure morphogenesis Source: ProtInc
  • blood coagulation Source: Reactome
  • bone resorption Source: Ensembl
  • cell adhesion Source: ProtInc
  • cell-matrix adhesion Source: BHF-UCL
  • cell motility Source: UniProtKB
  • cell proliferation Source: Ensembl
  • cellular response to mechanical stimulus Source: Ensembl
  • ephrin receptor signaling pathway Source: Reactome
  • Fc-epsilon receptor signaling pathway Source: Reactome
  • Fc-gamma receptor signaling pathway involved in phagocytosis Source: Reactome
  • hepatocyte growth factor receptor signaling pathway Source: CAFA
  • inflammatory response Source: ProtInc
  • intracellular signal transduction Source: ProtInc
  • lamellipodium assembly Source: UniProtKB
  • localization within membrane Source: BHF-UCL
  • mast cell chemotaxis Source: Ensembl
  • movement of cell or subcellular component Source: ProtInc
  • negative regulation of interleukin-23 production Source: BHF-UCL
  • negative regulation of receptor-mediated endocytosis Source: UniProtKB
  • neutrophil degranulation Source: Reactome
  • platelet activation Source: Reactome
  • positive regulation of apoptotic process Source: Reactome
  • positive regulation of cell-substrate adhesion Source: UniProtKB
  • positive regulation of DNA replication Source: Ensembl
  • positive regulation of focal adhesion assembly Source: UniProtKB
  • positive regulation of lamellipodium assembly Source: MGI
  • positive regulation of microtubule polymerization Source: CAFA
  • positive regulation of neutrophil chemotaxis Source: UniProtKB
  • positive regulation of protein phosphorylation Source: UniProtKB
  • positive regulation of Rho protein signal transduction Source: UniProtKB
  • positive regulation of stress fiber assembly Source: UniProtKB
  • positive regulation of substrate adhesion-dependent cell spreading Source: UniProtKB
  • Rac protein signal transduction Source: Ensembl
  • regulation of cell migration Source: UniProtKB
  • regulation of cell size Source: UniProtKB
  • regulation of defense response to virus by virus Source: Reactome
  • regulation of hydrogen peroxide metabolic process Source: BHF-UCL
  • regulation of lamellipodium assembly Source: CAFA
  • regulation of respiratory burst Source: BHF-UCL
  • regulation of small GTPase mediated signal transduction Source: Reactome
  • regulation of stress fiber assembly Source: CAFA
  • response to wounding Source: ProtInc
  • ruffle organization Source: MGI
  • semaphorin-plexin signaling pathway Source: UniProtKB
  • substrate adhesion-dependent cell spreading Source: UniProtKB
  • T cell costimulation Source: Reactome
  • vascular endothelial growth factor receptor signaling pathway Source: Reactome
  • Wnt signaling pathway, planar cell polarity pathway Source: Reactome


LigandGTP-binding, Nucleotide-binding

Enzyme and pathway databases

ReactomeiR-HSA-114604. GPVI-mediated activation cascade.
R-HSA-1433557. Signaling by SCF-KIT.
R-HSA-1445148. Translocation of GLUT4 to the plasma membrane.
R-HSA-164944. Nef and signal transduction.
R-HSA-193648. NRAGE signals death through JNK.
R-HSA-194840. Rho GTPase cycle.
R-HSA-2029482. Regulation of actin dynamics for phagocytic cup formation.
R-HSA-2424491. DAP12 signaling.
R-HSA-2871796. FCERI mediated MAPK activation.
R-HSA-376172. DSCAM interactions.
R-HSA-389359. CD28 dependent Vav1 pathway.
R-HSA-3928662. EPHB-mediated forward signaling.
R-HSA-3928664. Ephrin signaling.
R-HSA-3928665. EPH-ephrin mediated repulsion of cells.
R-HSA-399954. Sema3A PAK dependent Axon repulsion.
R-HSA-399955. SEMA3A-Plexin repulsion signaling by inhibiting Integrin adhesion.
R-HSA-4086400. PCP/CE pathway.
R-HSA-416482. G alpha (12/13) signalling events.
R-HSA-416550. Sema4D mediated inhibition of cell attachment and migration.
R-HSA-416572. Sema4D induced cell migration and growth-cone collapse.
R-HSA-418885. DCC mediated attractive signaling.
R-HSA-428540. Activation of Rac.
R-HSA-428543. Inactivation of Cdc42 and Rac.
R-HSA-4420097. VEGFA-VEGFR2 Pathway.
R-HSA-445144. Signal transduction by L1.
R-HSA-5218920. VEGFR2 mediated vascular permeability.
R-HSA-5625740. RHO GTPases activate PKNs.
R-HSA-5625900. RHO GTPases activate CIT.
R-HSA-5625970. RHO GTPases activate KTN1.
R-HSA-5626467. RHO GTPases activate IQGAPs.
R-HSA-5627123. RHO GTPases activate PAKs.
R-HSA-5663213. RHO GTPases Activate WASPs and WAVEs.
R-HSA-5663220. RHO GTPases Activate Formins.
R-HSA-5668599. RHO GTPases Activate NADPH Oxidases.
R-HSA-5687128. MAPK6/MAPK4 signaling.
R-HSA-6798695. Neutrophil degranulation.
R-HSA-8849471. PTK6 Regulates RHO GTPases, RAS GTPase and MAP kinases.
R-HSA-8875555. MET activates RAP1 and RAC1.
R-HSA-983231. Factors involved in megakaryocyte development and platelet production.

Names & Taxonomyi

Protein namesi
Recommended name:
Ras-related C3 botulinum toxin substrate 1
Alternative name(s):
Cell migration-inducing gene 5 protein
Ras-like protein TC25
Gene namesi
ORF Names:MIG5
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
  • UP000005640 Componenti: Chromosome 7

Organism-specific databases


Subcellular locationi

GO - Cellular componenti

  • cytoplasm Source: UniProtKB
  • cytoplasmic ribonucleoprotein granule Source: ParkinsonsUK-UCL
  • cytosol Source: UniProtKB
  • dendritic spine Source: SynGO
  • endoplasmic reticulum membrane Source: Reactome
  • extracellular exosome Source: UniProtKB
  • extracellular matrix Source: BHF-UCL
  • ficolin-1-rich granule membrane Source: Reactome
  • focal adhesion Source: UniProtKB
  • Golgi membrane Source: Ensembl
  • lamellipodium Source: UniProtKB
  • melanosome Source: UniProtKB-SubCell
  • membrane Source: UniProtKB
  • plasma membrane Source: Reactome
  • secretory granule membrane Source: Reactome
  • trans-Golgi network Source: FlyBase

Keywords - Cellular componenti

Cell membrane, Cytoplasm, Membrane

Pathology & Biotechi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Mutagenesisi12G → V: Constitutively active. Interacts with PARD6 proteins. Increases nuclear localization and up-regulates transcriptional activity of NR3C2. 2 Publications1
Mutagenesisi17T → N: Constitutively inactivated. Abolishes interaction with PARD6 proteins. No effect on NR3C2 transcriptional activity. No interaction with PPP5C. Doesn't activate PPP5C phosphatase activity and translocate PPP5C to the plasma membrane. 3 Publications1
Mutagenesisi30G → V: No interaction with PPP5C; when associated with L-61. Translocates to the plasma membrane; also when associated with L-61. 1 Publication1
Mutagenesisi32Y → F: Abolishes AMPylation by Haemophilus IbpA. 1 Publication1
Mutagenesisi35T → A: Abolishes AMPylation by Vibrio VopS. 2 Publications1
Mutagenesisi35T → S: No interaction with PPP5C; when associated with L-61. Translocates to the plasma membrane; also when associated with L-61. 2 Publications1
Mutagenesisi37F → A: Strongly reduced interaction with PLCB2. 1 Publication1
Mutagenesisi56W → A: Strongly reduced interaction with PLCB2. 1 Publication1
Mutagenesisi61Q → L: Constitutively active. Interacts with PARD6 proteins. Interacts with PPP5C, activates its phosphatase activity and translocates PPP5C to the plasma membrane. No effect on interaction with RAPH1. No interaction with PPP5C; when associated with V-30 or S-35. Translocates to the plasma membrane; also when associated with V-30 or S-35. 3 Publications1
Mutagenesisi67L → A: Strongly reduced interaction with PLCB2. 1 Publication1
Mutagenesisi70L → A: Strongly reduced interaction with PLCB2. 1 Publication1

Organism-specific databases


Chemistry databases

DrugBankiDB00514. Dextromethorphan.
DB04315. Guanosine-5'-Diphosphate.

Polymorphism and mutation databases


PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00000420361 – 189Ras-related C3 botulinum toxin substrate 1Add BLAST189
PropeptideiPRO_0000042037190 – 192Removed in mature formBy similarity3

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Modified residuei32O-AMP-tyrosine; by Haemophilus IbpA; alternate1 Publication1
Glycosylationi32O-linked (GlcNAc) tyrosine; by Photorhabdus PAU_02230; alternate1 Publication1
Modified residuei35O-AMP-threonine; by Vibrio VopS1 Publication1
Modified residuei39ADP-ribosylasparagine; by botulinum toxinBy similarity1
Cross-linki147Glycyl lysine isopeptide (Lys-Gly) (interchain with G-Cter in ubiquitin)1 Publication
Modified residuei189Cysteine methyl esterBy similarity1
Lipidationi189S-geranylgeranyl cysteine1 Publication1
Isoform B (identifier: P63000-2)
Modified residuei71PhosphoserineCombined sources1

Post-translational modificationi

(Microbial infection) AMPylation at Tyr-32 and Thr-35 are mediated by bacterial enzymes in case of infection by H.somnus and V.parahaemolyticus, respectively. AMPylation occurs in the effector region and leads to inactivation of the GTPase activity by preventing the interaction with downstream effectors, thereby inhibiting actin assembly in infected cells. It is unclear whether some human enzyme mediates AMPylation; FICD has such ability in vitro but additional experiments remain to be done to confirm results in vivo.2 Publications
GTP-bound active form is ubiquitinated by HACE1, leading to its degradation by the proteasome.2 Publications
(Microbial infection) Glycosylated at Tyr-32 by Photorhabdus asymbiotica toxin PAU_02230. Mono-O-GlcNAcylation by PAU_02230 inhibits downstream signaling by an impaired interaction with diverse regulator and effector proteins of Rac and leads to actin disassembly.1 Publication

Keywords - PTMi

ADP-ribosylation, Glycoprotein, Isopeptide bond, Lipoprotein, Methylation, Phosphoprotein, Prenylation, Ubl conjugation

Proteomic databases


PTM databases


Miscellaneous databases



Tissue specificityi

Isoform B is predominantly identified in skin and epithelial tissues from the intestinal tract. Its expression is elevated in colorectal tumors at various stages of neoplastic progression, as compared to their respective adjacent tissues.

Gene expression databases

ExpressionAtlasiP63000. baseline and differential.
GenevisibleiP63000. HS.

Organism-specific databases



Subunit structurei

Interacts with NISCH. Interacts with PIP5K1A. Interacts with the GTP-bound form of RAB7A. Interacts with SRGAP2. Interacts with CYFIP1/SRA-1. Interacts with PLXNB3. Interacts with ARHGDIA; the interaction is induced by SEMA5A, mediated through PLXNB3 and inactivates and stabilizes RAC1. Interacts (GTP-bound form preferentially) with PKN2 (via the REM repeats); the interaction stimulates autophosphorylation and phosphorylation of PKN2. Interacts with the GEF proteins PREX1, RASGRF2, FARP1, FARP2, DOCK1, DOCK2 and DOCK7, which promote the exchange between GDP and GTP, and therefore activate it. Interacts with PARD6A, PARD6B and PARD6G in a GTP-dependent manner. Part of a quaternary complex containing PARD3, some PARD6 protein (PARD6A, PARD6B or PARD6G) and some atypical PKC protein (PRKCI or PRKCZ), which plays a central role in epithelial cell polarization. Found in a trimeric complex composed of DOCK1 and ELMO1, which plays a central role in phagocytosis of apoptotic cells. Interacts with RALBP1 via its effector domain. Interacts with PLXNB1. Probably found in a ternary complex composed of DSCAM, PAK1 and RAC1. Interacts with DSCAM; the interaction requires PAK1. Part of a complex with MAP2K3, MAP3K3, CCM2 and DEF6. Interacts with BAIAP2, BAIAP2L1 and DEF6. Interacts with Y.pseudotuberculosis YPKA and PLCB2. Interacts with NOXA1. Interacts with ARHGEF2. Interacts with TBC1D2. Interacts with UNKL. Interacts with USP6. Interacts with SPATA13. Interacts with ARHGEF16; mediates activation of RAC1 by EPHA2. Interacts with ITGB4. Interacts with S100A8 and calprotectin (S100A8/9). Interacts with PACSIN2. Interacts with ITGB1BP1. Interacts (when active) with PPP5C (via TPR repeats); activates PPP5C phosphatase activity and translocates PPP5C to the cell membrane. Interacts with RAPH1 (via Ras associating and PH domains) (PubMed:18499456). Interacts with MTSS1L (via IMD domain); this interaction may be important to potentiate PDGF-induced RAC1 activation (PubMed:20875796).40 Publications

Binary interactionsi

Show more details

GO - Molecular functioni

  • ATPase binding Source: Ensembl
  • enzyme binding Source: BHF-UCL
  • histone deacetylase binding Source: Ensembl
  • protein kinase binding Source: CAFA
  • Rab GTPase binding Source: Ensembl
  • Rho GDP-dissociation inhibitor binding Source: UniProtKB
  • thioesterase binding Source: UniProtKB

Protein-protein interaction databases

BioGridi111817. 170 interactors.
IntActiP63000. 124 interactors.

Chemistry databases



Secondary structure

Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Beta strandi2 – 9Combined sources8
Helixi12 – 14Combined sources3
Helixi16 – 25Combined sources10
Beta strandi31 – 36Combined sources6
Beta strandi39 – 46Combined sources8
Beta strandi49 – 56Combined sources8
Helixi62 – 64Combined sources3
Turni65 – 67Combined sources3
Helixi68 – 71Combined sources4
Beta strandi76 – 83Combined sources8
Helixi87 – 95Combined sources9
Helixi97 – 104Combined sources8
Beta strandi106 – 108Combined sources3
Beta strandi110 – 115Combined sources6
Helixi117 – 120Combined sources4
Helixi123 – 131Combined sources9
Helixi139 – 148Combined sources10
Beta strandi152 – 156Combined sources5
Turni159 – 161Combined sources3
Helixi165 – 176Combined sources12

3D structure databases

Select the link destinations:
Links Updated
PDB entryMethodResolution (Å)ChainPositionsPDBsum

Miscellaneous databases


Family & Domainsi


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Motifi32 – 40Effector regionSequence analysis9


The effector region mediates interaction with DEF6.1 Publication

Sequence similaritiesi

Belongs to the small GTPase superfamily. Rho family.Curated

Phylogenomic databases


Family and domain databases

InterProiView protein in InterPro
IPR027417. P-loop_NTPase.
IPR005225. Small_GTP-bd_dom.
IPR001806. Small_GTPase.
IPR003578. Small_GTPase_Rho.
PfamiView protein in Pfam
PF00071. Ras. 1 hit.
SUPFAMiSSF52540. SSF52540. 1 hit.
TIGRFAMsiTIGR00231. small_GTP. 1 hit.
PROSITEiView protein in PROSITE
PS51420. RHO. 1 hit.

Sequences (2)i

Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

This entry describes 2 isoformsi produced by alternative splicing. AlignAdd to basket

Isoform A (identifier: P63000-1) [UniParc]FASTAAdd to basket
Also known as: Rac1A

This isoform has been chosen as the 'canonical' sequence. All positional information in this entry refers to it. This is also the sequence that appears in the downloadable versions of the entry.

« Hide

        10         20         30         40         50
60 70 80 90 100
110 120 130 140 150
160 170 180 190
Mass (Da):21,450
Last modified:August 31, 2004 - v1
Isoform B (identifier: P63000-2) [UniParc] [UniParc]FASTAAdd to basket
Also known as: Rac1B, Rac1ins

The sequence of this isoform differs from the canonical sequence as follows:

Show »
Mass (Da):23,467

Sequence cautioni

The sequence AAZ80485 differs from that shown. Reason: Erroneous initiation. Translation N-terminally extended.Curated

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti192Missing in AAA36544 (PubMed:2108320).Curated1

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_01454026N → D. Corresponds to variant dbSNP:rs5830Ensembl.1
Natural variantiVAR_01454128F → L. Corresponds to variant dbSNP:rs5832Ensembl.1
Natural variantiVAR_01454259A → T. Corresponds to variant dbSNP:rs5837Ensembl.1
Natural variantiVAR_01454363D → G. Corresponds to variant dbSNP:rs5831Ensembl.1
Natural variantiVAR_01454593V → G. Corresponds to variant dbSNP:rs5826Ensembl.1
Natural variantiVAR_01454493V → I. Corresponds to variant dbSNP:rs5825Ensembl.1
Natural variantiVAR_014546108T → I. Corresponds to variant dbSNP:rs5838Ensembl.1
Natural variantiVAR_014547130K → R. Corresponds to variant dbSNP:rs5828Ensembl.1
Natural variantiVAR_014548133K → E. Corresponds to variant dbSNP:rs5835Ensembl.1
Natural variantiVAR_033303135T → I1 PublicationCorresponds to variant dbSNP:rs11540455Ensembl.1
Natural variantiVAR_014549180P → S. Corresponds to variant dbSNP:rs16063Ensembl.1
Natural variantiVAR_014550182V → E. Corresponds to variant dbSNP:rs5836Ensembl.1

Alternative sequence

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Alternative sequenceiVSP_00571075T → TVGETYGKDITSRGKDKPIA in isoform B. 3 Publications1

Sequence databases

Select the link destinations:
Links Updated
M29870 mRNA. Translation: AAA36537.1.
M31467 mRNA. Translation: AAA36544.1.
AJ132694 mRNA. Translation: CAA10732.1.
AJ132695 Genomic DNA. Translation: CAB53579.5.
AJ132695 Genomic DNA. Translation: CAA10733.6.
AF136373 mRNA. Translation: AAD30547.1.
AY279384 mRNA. Translation: AAQ16632.1.
AF498964 mRNA. Translation: AAM21111.1.
BT007121 mRNA. Translation: AAP35785.1.
DQ165078 Genomic DNA. Translation: AAZ80485.1. Different initiation.
AC009412 Genomic DNA. Translation: AAS07511.1.
AC009412 Genomic DNA. Translation: AAS07512.1.
BC004247 mRNA. Translation: AAH04247.1.
BC050687 mRNA. Translation: AAH50687.1.
BC107748 mRNA. Translation: AAI07749.1.
CCDS5349.1. [P63000-2]
PIRiA34788. TVHUC1.
RefSeqiNP_008839.2. NM_006908.4. [P63000-1]
NP_061485.1. NM_018890.3. [P63000-2]

Genome annotation databases

EnsembliENST00000348035; ENSP00000258737; ENSG00000136238. [P63000-1]
ENST00000356142; ENSP00000348461; ENSG00000136238. [P63000-2]
UCSCiuc003spw.4. human.

Keywords - Coding sequence diversityi

Alternative splicing, Polymorphism

Similar proteinsi

Links to similar proteins from the UniProt Reference Clusters (UniRef) at 100%, 90% and 50% sequence identity:
100%UniRef100 combines identical sequences and sub-fragments with 11 or more residues from any organism into one UniRef entry.
90%UniRef90 is built by clustering UniRef100 sequences that have at least 90% sequence identity to, and 80% overlap with, the longest sequence (a.k.a seed sequence).
50%UniRef50 is built by clustering UniRef90 seed sequences that have at least 50% sequence identity to, and 80% overlap with, the longest sequence in the cluster.

Entry informationi

Entry nameiRAC1_HUMAN
AccessioniPrimary (citable) accession number: P63000
Secondary accession number(s): O95501
, P15154, Q3Y4D3, Q5JAA8, Q9BTB4
Entry historyiIntegrated into UniProtKB/Swiss-Prot: August 31, 2004
Last sequence update: August 31, 2004
Last modified: July 5, 2017
This is version 169 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program
DisclaimerAny 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.


Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome


  1. Human chromosome 7
    Human chromosome 7: entries, gene names and cross-references to MIM
  2. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  3. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  4. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  5. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  6. SIMILARITY comments
    Index of protein domains and families