Summary: Alpha-2-macroglobulin family
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Alpha-2-Macroglobulin Edit Wikipedia article
|, A2MD, CPAMD5, FWP007, S863-7, transcuprein, alpha-2-macroglobulin|
alpha-2-Macroglobulin (Î±2M) is a large (720 KDa) plasma protein found in the blood. It is mainly produced by the liver, and also locally synthesized by macrophages, fibroblasts, and adrenocortical cells. In humans it is encoded by the A2M gene.
Alpha 2 macroglobulin acts as an antiprotease and is able to inactivate an enormous variety of proteinases. It functions as an inhibitor of fibrinolysis by inhibiting plasmin and kallikrein. It functions as an inhibitor of coagulation by inhibiting thrombin. Alpha-2-macroglobulin may act as a carrier protein because it also binds to numerous growth factors and cytokines, such as platelet-derived growth factor, basic fibroblast growth factor, TGF-Î², insulin, and IL-1Î².
No specific deficiency with associated disease has been recognized, and no disease state is attributed to low concentrations of alpha-2-macroglobulin. The concentration of alpha-2-macroglobulin rises 10-fold or more in the nephrotic syndrome when other lower molecular weight proteins are lost in the urine. The loss of alpha-2-macroglobulin into urine is prevented by its large size. The net result is that alpha-2-macroglobulin reaches serum levels equal to or greater than those of albumin in the nephrotic syndrome, which has the effect of maintaining oncotic pressure.
Human alpha-2-macroglobulin is composed of four identical subunits bound together by -S-S- bonds. In addition to tetrameric forms of alpha-2-macroglobulin, dimeric, and more recently monomeric aM protease inhibitors have been identified.
Each monomer of human alpha-2-macroglobulin is composed of several functional domains, including macroglobulin domains, a thiol ester-containing domain and a receptor-binding domain. Overall, alpha-2-Macroglobulin is the largest major nonimmunoglobulin protein in human plasma.
The alpha-macroglobulin (aM) family of proteins includes protease inhibitors, typified by the human tetrameric alpha-2-macroglobulin (a2M); they belong to the MEROPS proteinase inhibitor family I39, clan IL. These protease inhibitors share several defining properties, which include (i) the ability to inhibit proteases from all catalytic classes, (ii) the presence of a 'bait region' (aka. a sequence of amino acids in an Î±2-macroglobulin molecule, or a homologous protein, that contains scissile peptide bonds for those proteinases that it inhibits) and a thiol ester, (iii) a similar protease inhibitory mechanism and (iv) the inactivation of the inhibitory capacity by reaction of the thiol ester with small primary amines. aM protease inhibitors inhibit by steric hindrance. The mechanism involves protease cleavage of the bait region, a segment of the aM that is particularly susceptible to proteolytic cleavage, which initiates a conformational change such that the aM collapses about the protease. In the resulting aM-protease complex, the active site of the protease is sterically shielded, thus substantially decreasing access to protein substrates. Two additional events occur as a consequence of bait region cleavage, namely (i) the h-cysteinyl-g-glutamyl thiol ester becomes highly reactive and (ii) a major conformational change exposes a conserved COOH-terminal receptor binding domain  (RBD). RBD exposure allows the aM protease complex to bind to clearance receptors and be removed from circulation. Tetrameric, dimeric, and, more recently, monomeric aM protease inhibitors have been identified.
alpha-2-Macroglobulin is able to inactivate an enormous variety of proteinases (including serine-, cysteine-, aspartic- and metalloproteinases). It functions as an inhibitor of fibrinolysis by inhibiting plasmin and kallikrein. It functions as an inhibitor of coagulation by inhibiting thrombin. Alpha-2-macroglobulin has in its structure a 35 amino acid "bait" region. Proteinases binding and cleaving the bait region become bound to Î±2M. The proteinase-Î±2M complex is recognised by macrophage receptors and cleared from the system.
alpha-2-Macroglobulin is known to bind zinc, as well as copper in plasma, even more strongly than albumin, and such it is also known as transcuprein. 10-15% of copper in human plasma is chelated by alpha-2-macroglobulin.
alpha-2-Macroglobulin levels are increased when the serum albumin levels are low, which is most commonly seen in nephrotic syndrome, a condition wherein the kidneys start to leak out some of the smaller blood proteins. Because of its size, alpha-2-macroglobulin is retained in the bloodstream. Increased production of all proteins means alpha-2-macroglobulin concentration increases. This increase has little adverse effect on the health, but is used as a diagnostic clue. Longstanding chronic renal failure can lead to amyloid by alpha-2-macroglobulin (see main article: amyloid).
alpha-2-Macroglobulin binds to and removes the active forms of the gelatinase (MMP-2 and MMP-9) from the circulation via scavenger receptors on the phagocytes.
- GRCh38: Ensembl release 89: ENSG00000175899 - Ensembl, May 2017
- GRCm38: Ensembl release 89: ENSMUSG00000030111 - Ensembl, May 2017
- "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- Andersen GR, Koch TJ, Dolmer K, Sottrup-Jensen L, Nyborg J (October 1995). "Low resolution X-ray structure of human methylamine-treated alpha 2-macroglobulin". J. Biol. Chem. 270 (42): 25133â€“41. doi:10.1074/jbc.270.42.25133. PMID 7559647.
- Sottrup-Jensen L, Stepanik TM, Kristensen T, Wierzbicki DM, Jones CM, LÃ¸nblad PB, et al. (1984). "Primary structure of human alpha 2-macroglobulin. V. The complete structure". J Biol Chem. 259 (13): 8318â€“27. PMID 6203908.
- Dodds AW, Law SK (December 1998). "The phylogeny and evolution of the thioester bond-containing proteins C3, C4 and alpha 2-macroglobulin". Immunol. Rev. 166: 15â€“26. doi:10.1111/j.1600-065X.1998.tb01249.x. PMID 9914899.
- Armstrong PB, Quigley JP (1999). "Alpha2-macroglobulin: an evolutionarily conserved arm of the innate immune system". Dev. Comp. Immunol. 23 (4â€“5): 375â€“90. doi:10.1016/s0145-305x(99)00018-x. PMID 10426429.
- Doan N, Gettins PG (2007). "Human alpha2-macroglobulin is composed of multiple domains, as predicted by homology with complement component C3". Biochem J. 407 (1): 23â€“30. doi:10.1042/BJ20070764. PMC 2267405. PMID 17608619.
- Devriendt K, Van den Berghe H, Cassiman JJ, Marynen P (1991). â€œPrimary structure of pregnancy zone protein. Molecular cloning of a full-length PZP cDNA clone by the polymerase chain reactionâ€. Biochimica et Biophysica Acta. 1088(1): 95-103
- Sottrup-Jensen L (July 1989). "Alpha-macroglobulins: structure, shape, and mechanism of proteinase complex formation". J. Biol. Chem. 264 (20): 11539â€“42. PMID 2473064.
- Enghild JJ, Salvesen G, ThÃ¸gersen IB, Pizzo SV (July 1989). "Proteinase binding and inhibition by the monomeric alpha-macroglobulin rat alpha 1-inhibitor-3". J. Biol. Chem. 264 (19): 11428â€“35. PMID 2472396.
- Enghild JJ, ThÃ¸gersen IB, Roche PA, Pizzo SV (February 1989). "A conserved region in alpha-macroglobulins participates in binding to the mammalian alpha-macroglobulin receptor". Biochemistry. 28 (3): 1406â€“12. doi:10.1021/bi00429a069. PMID 2469470.
- Van Leuven F, Cassiman JJ, Van den Berghe H (December 1986). "Human pregnancy zone protein and alpha 2-macroglobulin. High-affinity binding of complexes to the same receptor on fibroblasts and characterization by monoclonal antibodies". J. Biol. Chem. 261 (35): 16622â€“5. PMID 2430968.
- de Boer JP, Creasey AA, Chang A, Abbink JJ, Roem D, Eerenberg AJ, Hack CE, Taylor FB (December 1993). "Alpha-2-macroglobulin functions as an inhibitor of fibrinolytic, clotting, and neutrophilic proteinases in sepsis: studies using a baboon model". Infect. Immun. 61 (12): 5035â€“43. PMC 281280. PMID 7693593.
- Liu, Nanmei; Lo, Louis Shi-li; Askary, S. Hassan; Jones, LaTrice; Kidane, Theodros Z.; Nguyen, Trisha Trang Minh; Goforth, Jeremy; Chu, Yu-Hsiang; Vivas, Esther; Tsai, Monta; Westbrook, Terence; Linder, Maria C. (September 2007). "Transcuprein is a macroglobulin regulated by copper and iron availability". The Journal of Nutritional Biochemistry. 18 (9): 597â€“608. doi:10.1016/j.jnutbio.2006.11.005. PMC 4286573. PMID 17363239.
- Liu, Nan-mei; Nguyen, Trang; Kidane, Theodros; Moriya, Mizue; Goforth, Jeremy; Chu, Andy; Linder, Maria (6 March 2006). "Transcupreins are serum copper-transporters of the macroglobulin family, and may be regulated by iron and copper". The FASEB Journal. 20 (4): A553â€“A554. doi:10.1096/fasebj.20.4.A553-d. ISSN 0892-6638.
- Stevenson, FT; Greene, S; Kaysen, GA (January 1998). "Serum alpha 2-macroglobulin and alpha 1-inhibitor 3 concentrations are increased in hypoalbuminemia by post-transcriptional mechanisms". Kidney International. 53 (1): 67â€“75. doi:10.1046/j.1523-1755.1998.00734.x. PMID 9453001.
- Blacker D, Wilcox MA, Laird NM, Rodes L, Horvath SM, Go RC, Perry R, Watson B, Bassett SS, McInnis MG, Albert MS, Hyman BT, Tanzi RE (August 1998). "Alpha-2 macroglobulin is genetically associated with Alzheimer disease". Nat. Genet. 19 (4): 357â€“60. doi:10.1038/1243. PMID 9697696.
- Kovacs DM (July 2000). "alpha2-macroglobulin in late-onset Alzheimer's disease". Exp. Gerontol. 35 (4): 473â€“9. doi:10.1016/S0531-5565(00)00113-3. PMID 10959035.
- McPherson & Pincus: Henry's Clinical Diagnosis and Management by Laboratory Methods, 21st ed.
- Firestein: Kelley's Textbook of Rheumatology, 8th edition.
This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.
Alpha-2-macroglobulin family Provide feedback
This family includes the C-terminal region of the alpha-2-macroglobulin family.
Zanotti G, Bassetto A, Battistutta R, Folli C, Arcidiaco P, Stoppini M, Berni R; , Biochim Biophys Acta 2000;1478:232-238.: Structure at 1.44 A resolution of an N-terminally truncated form of the rat serum complement C3d fragment. PUBMED:10825534 EPMC:10825534
Internal database links
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR001599
This entry contains serum complement C3 and C4 precursors and alpha-macrogrobulins.
The alpha-macroglobulin (aM) family of proteins includes protease inhibitors [PUBMED:2473064], typified by the human tetrameric a2-macroglobulin (a2M); they belong to the MEROPS proteinase inhibitor family I39, clan IL. These protease inhibitors share several defining properties, which include (i) the ability to inhibit proteases from all catalytic classes, (ii) the presence of a 'bait region' and a thiol ester, (iii) a similar protease inhibitory mechanism and (iv) the inactivation of the inhibitory capacity by reaction of the thiol ester with small primary amines. aM protease inhibitors inhibit by steric hindrance [PUBMED:2472396]. The mechanism involves protease cleavage of the bait region, a segment of the aM that is particularly susceptible to proteolytic cleavage, which initiates a conformational change such that the aM collapses about the protease. In the resulting aM-protease complex, the active site of the protease is sterically shielded, thus substantially decreasing access to protein substrates. Two additional events occur as a consequence of bait region cleavage, namely (i) the h-cysteinyl-g-glutamyl thiol ester becomes highly reactive and (ii) a major conformational change exposes a conserved COOH-terminal receptor binding domain [PUBMED:2469470] (RBD). RBD exposure allows the aM protease complex to bind to clearance receptors and be removed from circulation [PUBMED:2430968]. Tetrameric, dimeric, and, more recently, monomeric aM protease inhibitors have been identified [PUBMED:9914899, PUBMED:10426429].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||endopeptidase inhibitor activity (GO:0004866)|
Below is a listing of the unique domain organisations or architectures in which this domain is found. More...
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This clan includes a diverse range of domains that have an Ig-like fold and appear to be distantly related to each other. The clan includes: PKD domains, cadherins and several families of bacterial Ig-like domains as well as viral tail fibre proteins. it also includes several Fibronectin type III domain-containing families.
The clan contains the following 233 members:A2M A2M_BRD A2M_recep Adeno_GP19K AlcCBM31 Alpha-amylase_N Alpha_adaptinC2 Alpha_E2_glycop Arch_flagellin aRib Arylsulfotran_N ASF1_hist_chap ATG19_autophagy BACON BACON_2 BatD BIg21 Big_1 Big_10 Big_11 Big_12 Big_13 Big_2 Big_3 Big_3_2 Big_3_3 Big_3_4 Big_3_5 Big_4 Big_5 Big_6 Big_7 Big_8 Big_9 Bile_Hydr_Trans BiPBP_C bMG1 bMG10 bMG3 bMG5 bMG6 BslA BsuPI Cadherin Cadherin-like Cadherin_2 Cadherin_3 Cadherin_4 Cadherin_5 Cadherin_pro CagX Calx-beta Candida_ALS_N CARDB CBM39 CBM_X2 CD45 CelD_N Ceramidse_alk_C CHB_HEX_C CHB_HEX_C_1 ChitinaseA_N ChiW_Ig_like Chlam_OMP6 CHU_C Coatamer_beta_C COP-gamma_platf CopC CshA_repeat Cyc-maltodext_N Cytomega_US3 DsbC DUF11 DUF1410 DUF1425 DUF1929 DUF2271 DUF3244 DUF3327 DUF3416 DUF3458 DUF3501 DUF3823_C DUF3859 DUF4165 DUF4179 DUF4426 DUF4469 DUF4625 DUF4879 DUF4959 DUF4981 DUF4982 DUF4998 DUF5001 DUF5008 DUF5011 DUF5065 DUF5115 DUF525 DUF5643 DUF916 EB_dh ECD EpoR_lig-bind ERAP1_C EstA_Ig_like Expansin_C Filamin FixG_C Flavi_glycop_C FlgD_ig fn3 Fn3-like fn3_2 fn3_4 fn3_5 fn3_6 FN3_7 Fn3_assoc fn3_PAP GBS_Bsp-like Glucodextran_B Glyco_hydro2_C5 Glyco_hydro_2 Glyco_hydro_61 Gmad2 GMP_PDE_delta GPI-anchored Hanta_G1 He_PIG HECW_N HemeBinding_Shp Hemocyanin_C Herpes_BLLF1 HYR IFNGR1 Ig_GlcNase Ig_mannosidase IL12p40_C Il13Ra_Ig IL17R_fnIII_D1 IL17R_fnIII_D2 IL2RB_N1 IL3Ra_N IL4Ra_N IL6Ra-bind Inhibitor_I42 Inhibitor_I71 InlK_D3 Integrin_alpha2 Interfer-bind Invasin_D3 IRK_C IrmA Iron_transport LEA_2 Lep_receptor_Ig LIFR_N Lipase_bact_N LPMO_10 LRR_adjacent LTD Mannosidase_ig MetallophosC MG1 MG2 MG3 MG4 Mo-co_dimer N_BRCA1_IG Na_K-ATPase NEAT Neocarzinostat Neurexophilin NPCBM_assoc PapD_C PBP-Tp47_c Peptidase_C25_C Phlebo_G2_C PhoD_N PKD PKD_2 PKD_3 PKD_4 Por_Secre_tail Pox_vIL-18BP Psg1 Pur_ac_phosph_N Qn_am_d_aII Qn_am_d_aIII RabGGT_insert Reeler REJ RET_CLD1 RET_CLD3 RET_CLD4 RGI_lyase RHD_dimer Rho_GDI Rib RibLong SCAB-Ig SKICH SLAM SoxZ SprB SusE SVA SWM_repeat T2SS-T3SS_pil_N Tafi-CsgC TarS_C1 TcA_RBD TcfC TIG TIG_2 TIG_plexin Tissue_fac Top6b_C Transglut_C Transglut_N TRAP_beta TraQ_transposon Tuberculin UL16 Velvet WIF Wzt_C Y_Y_Y YBD ZirS_C Zona_pellucida
We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the UniProtKB sequence database, the NCBI sequence database, and our metagenomics sequence database. More...
There are various ways to view or download the sequence alignments that we store. We provide several sequence viewers and a plain-text Stockholm-format file for download.
We make a range of alignments for each Pfam-A family:
- the curated alignment from which the HMM for the family is built
- the alignment generated by searching the sequence database using the HMM
- Representative Proteomes (RPs) at 15%, 35%, 55% and 75% co-membership thresholds
- alignment generated by searching the UniProtKB sequence database using the family HMM
- alignment generated by searching the NCBI sequence database using the family HMM
- alignment generated by searching the metagenomics sequence database using the family HMM
You can see the alignments as HTML or in three different sequence viewers:
- a Java applet developed at the University of Dundee. You will need Java installed before running jalview
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You can download (or view in your browser) a text representation of a Pfam alignment in various formats:
You can also change the order in which sequences are listed in the alignment, change how insertions are represented, alter the characters that are used to represent gaps in sequences and, finally, choose whether to download the alignment or to view it in your browser directly.
You may find that large alignments cause problems for the viewers and the reformatting tool, so we also provide all alignments in Stockholm format. You can download either the plain text alignment, or a gzipped version of it.
We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
Key: available, not generated, — not available.
Format an alignment
We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.
You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.
HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...
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This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.
Note: You can also download the data file for the tree.
Curation and family details
This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.
|Author:||Finn RD , Sammut SJ|
|Number in seed:||73|
|Number in full:||6261|
|Average length of the domain:||90.00 aa|
|Average identity of full alignment:||24 %|
|Average coverage of the sequence by the domain:||5.69 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 47079205 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||23|
|Download:||download the raw HMM for this family|
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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the More....
This chart is a modified "sunburst" visualisation of the species tree for this family. It shows each node in the tree as a separate arc, arranged radially with the superkingdoms at the centre and the species arrayed around the outermost ring.
How the sunburst is generated
The tree is built by considering the taxonomic lineage of each sequence that has a match to this family. For each node in the resulting tree, we draw an arc in the sunburst. The radius of the arc, its distance from the root node at the centre of the sunburst, shows the taxonomic level ("superkingdom", "kingdom", etc). The length of the arc represents either the number of sequences represented at a given level, or the number of species that are found beneath the node in the tree. The weighting scheme can be changed using the sunburst controls.
In order to reduce the complexity of the representation, we reduce the number of taxonomic levels that we show. We consider only the following eight major taxonomic levels:
Colouring and labels
Segments of the tree are coloured approximately according to their superkingdom. For example, archeal branches are coloured with shades of orange, eukaryotes in shades of purple, etc. The colour assignments are shown under the sunburst controls. Where space allows, the name of the taxonomic level will be written on the arc itself.
As you move your mouse across the sunburst, the current node will be highlighted. In the top section of the controls panel we show a summary of the lineage of the currently highlighed node. If you pause over an arc, a tooltip will be shown, giving the name of the taxonomic level in the title and a summary of the number of sequences and species below that node in the tree.
Anomalies in the taxonomy tree
There are some situations that the sunburst tree cannot easily handle and for which we have work-arounds in place.
Missing taxonomic levels
Some species in the taxonomic tree may not have one or more of the main eight levels that we display. For example, Bos taurus is not assigned an order in the NCBI taxonomic tree. In such cases we mark the omitted level with, for example, "No order", in both the tooltip and the lineage summary.
Unmapped species names
The tree is built by looking at each sequence in the full alignment for the family. We take the name of the species given by UniProt and try to map that to the full taxonomic tree from NCBI. In some cases, the name chosen by UniProt does not map to any node in the NCBI tree, perhaps because the chosen name is listed as a synonym or a misspelling in the NCBI taxonomy.
So that these nodes are not simply omitted from the sunburst tree, we group them together in a separate branch (or segment of the sunburst tree). Since we cannot determine the lineage for these unmapped species, we show all levels between the superkingdom and the species as "uncategorised".
Since we reduce the species tree to only the eight main taxonomic levels, sequences that are mapped to the sub-species level in the tree would not normally be shown. Rather than leave out these species, we map them instead to their parent species. So, for example, for sequences belonging to one of the Vibrio cholerae sub-species in the NCBI taxonomy, we show them instead as belonging to the species Vibrio cholerae.
Too many species/sequences
For large species trees, you may see blank regions in the outer layers of the sunburst. These occur when there are large numbers of arcs to be drawn in a small space. If an arc is less than approximately one pixel wide, it will not be drawn and the space will be left blank. You may still be able to get some information about the species in that region by moving your mouse across the area, but since each arc will be very small, it will be difficult to accurately locate a particular species.
The tree shows the occurrence of this domain across different species. More...
We show the species tree in one of two ways. For smaller trees we try to show an interactive representation, which allows you to select specific nodes in the tree and view them as an alignment or as a set of Pfam domain graphics.
Unfortunately we have found that there are problems viewing the interactive tree when the it becomes larger than a certain limit. Furthermore, we have found that Internet Explorer can become unresponsive when viewing some trees, regardless of their size. We therefore show a text representation of the species tree when the size is above a certain limit or if you are using Internet Explorer to view the site.
If you are using IE you can still load the interactive tree by clicking the "Generate interactive tree" button, but please be aware of the potential problems that the interactive species tree can cause.
For all of the domain matches in a full alignment, we count the number that are found on all sequences in the alignment. This total is shown in the purple box.
We also count the number of unique sequences on which each domain is found, which is shown in green. Note that a domain may appear multiple times on the same sequence, leading to the difference between these two numbers.
Finally, we group sequences from the same organism according to the NCBI code that is assigned by UniProt, allowing us to count the number of distinct sequences on which the domain is found. This value is shown in the pink boxes.
We use the NCBI species tree to group organisms according to their taxonomy and this forms the structure of the displayed tree. Note that in some cases the trees are too large (have too many nodes) to allow us to build an interactive tree, but in most cases you can still view the tree in a plain text, non-interactive representation. Those species which are represented in the seed alignment for this domain are highlighted.
You can use the tree controls to manipulate how the interactive tree is displayed:
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Please note: for large trees this can take some time. While the tree is loading, you can safely switch away from this tab but if you browse away from the family page entirely, the tree will not be loaded.
There are 16 interactions for this family. More...
We determine these interactions using iPfam, which considers the interactions between residues in three-dimensional protein structures and maps those interactions back to Pfam families. You can find more information about the iPfam algorithm in the journal article that accompanies the website.
For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the A2M domain has been found. There are 103 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.
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