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145  structures 8889  species 0  interactions 13942  sequences 108  architectures

Family: tRNA-synt_2d (PF01409)

Summary: tRNA synthetases class II core domain (F)

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tRNA synthetases class II core domain (F) Provide feedback

Other tRNA synthetase sub-families are too dissimilar to be included. This family includes only phenylalanyl-tRNA synthetases. This is the core catalytic domain.

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR002319

The aminoacyl-tRNA synthetases (also known as aminoacyl-tRNA ligases) catalyse the attachment of an amino acid to its cognate transfer RNA molecule in a highly specific two-step reaction [ PUBMED:10704480 , PUBMED:12458790 ]. These proteins differ widely in size and oligomeric state, and have limited sequence homology [ PUBMED:2203971 ]. The 20 aminoacyl-tRNA synthetases are divided into two classes, I and II. Class I aminoacyl-tRNA synthetases contain a characteristic Rossman fold catalytic domain and are mostly monomeric [ PUBMED:10673435 ]. Class II aminoacyl-tRNA synthetases share an anti-parallel beta-sheet fold flanked by alpha-helices [ PUBMED:8364025 ], and are mostly dimeric or multimeric, containing at least three conserved regions [ PUBMED:8274143 , PUBMED:2053131 , PUBMED:1852601 ]. However, tRNA binding involves an alpha-helical structure that is conserved between class I and class II synthetases. In reactions catalysed by the class I aminoacyl-tRNA synthetases, the aminoacyl group is coupled to the 2'-hydroxyl of the tRNA, while, in class II reactions, the 3'-hydroxyl site is preferred. The synthetases specific for arginine, cysteine, glutamic acid, glutamine, isoleucine, leucine, methionine, tyrosine, tryptophan, valine, and some lysine synthetases (non-eukaryotic group) belong to class I synthetases. The synthetases specific for alanine, asparagine, aspartic acid, glycine, histidine, phenylalanine, proline, serine, threonine, and some lysine synthetases (non-archaeal group), belong to class-II synthetases. Based on their mode of binding to the tRNA acceptor stem, both classes of tRNA synthetases have been subdivided into three subclasses, designated 1a, 1b, 1c and 2a, 2b, 2c [ PUBMED:10447505 ].

Phenylalanyl-tRNA synthetase ( EC ) is an alpha2/beta2 tetramer composed of 2 subunits that belongs to class IIc. In eubacteria, a small subunit (pheS gene) can be designated as beta (E. coli) or alpha subunit (nomenclature adopted in InterPro). Reciprocally the large subunit (pheT gene) can be designated as alpha (E. coli) or beta (see INTERPRO and INTERPRO ). In all other kingdoms the two subunits have equivalent length in eukaryota, and can be identified by specific signatures. The enzyme from Thermus thermophilus has an alpha 2 beta 2 type quaternary structure and is one of the most complicated members of the synthetase family. Identification of phenylalanyl-tRNA synthetase as a member of class II aaRSs was based only on sequence alignment of the small alpha-subunit with other synthetases [ PUBMED:8199244 ].

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan tRNA_synt_II (CL0040), which has the following description:

Aminoacyl-tRNA synthetases are key components of the protein translation machinery that catalyse two basic reactions. First, the activation of amino acids via the formation of aminoacyl adenylates and second, linking the activated amino acid to the cognate tRNAs. The aminoacyl-tRNA synthetases generate AMP as the second end product of this reaction, which differentiates them from the majority of ATP-dependent enzymes that produce ADP. In addition, there is a specific aminoacyl-tRNA synthetases for each of the 20 amino acids and there are two structurally distinct classes of aminoacyl-tRNA synthetases, each encompassing 10 different specificities. The two classes have alternative modes of aminoacylation: class I aminoacylate the 2'OH of the cognate tRNA; class II aminoacylate 3'OH (with the exception of PheRS). Each class contain a conserved core domain that is involved in ATP binding and hydrolysis and combines with additional domains that determine the specificity of interactions with the cognate amino acid and tRNA. The class II core domain consist of a mixed-beta sheet, similar to that found in the biotin synthetases, hence why this family has also been included in this clan. The core domain contains three modestly conserved motifs that are responsible for ATP binding. The class II aminoacyl-tRNA synthetases can contain additional nested domains, found inserted in the loops of the core domain [1] (and reference therein).

The clan contains the following 11 members:

AsnA BPL_LplA_LipB BPL_LplA_LipB_2 DUF366 tRNA-synt_2 tRNA-synt_2b tRNA-synt_2c tRNA-synt_2d tRNA-synt_2e tRNA-synt_His tRNA_synthFbeta


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 and the UniProtKB sequence database. More...

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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.

Representative proteomes UniProt
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PP/heatmap 1            

1Cannot generate PP/Heatmap alignments for seeds; no PP data available

Key: ✓ available, x not generated, not available.

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Representative proteomes UniProt

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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.

Representative proteomes UniProt
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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

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...


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.

Curation View help on the curation process

Seed source: swissprot
Previous IDs: none
Type: Domain
Sequence Ontology: SO:0000417
Author: Howe K
Number in seed: 43
Number in full: 13942
Average length of the domain: 223.1 aa
Average identity of full alignment: 37 %
Average coverage of the sequence by the domain: 64.23 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 19.8 19.8
Trusted cut-off 19.8 19.8
Noise cut-off 19.7 19.7
Model length: 246
Family (HMM) version: 23
Download: download the raw HMM for this family

Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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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 adjacent tab. More...

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The tree shows the occurrence of this domain across different species. More...


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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 tRNA-synt_2d domain has been found. There are 145 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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AlphaFold Structure Predictions

The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.

Protein Predicted structure External Information
A0A077YX42 View 3D Structure Click here
A0A077Z553 View 3D Structure Click here
A0A077ZM91 View 3D Structure Click here
A0A0D2DUC5 View 3D Structure Click here
A0A0D2GFG8 View 3D Structure Click here
A0A0H3GU78 View 3D Structure Click here
A0A0K0DY20 View 3D Structure Click here
A0A0K0ECX8 View 3D Structure Click here
A0A0N4U4V0 View 3D Structure Click here
A0A0N4UGD3 View 3D Structure Click here
A0A0R0FHD2 View 3D Structure Click here
A0A175VVS0 View 3D Structure Click here
A0A175W8P2 View 3D Structure Click here
A0A1C1CNI0 View 3D Structure Click here
A0A1C1D0G5 View 3D Structure Click here
A0A1D6GCF3 View 3D Structure Click here
A0A1D6ND62 View 3D Structure Click here
A0A1D8PCT4 View 3D Structure Click here
A0A1P6BGA4 View 3D Structure Click here
A0A2K6VV45 View 3D Structure Click here
A0A2K6WD61 View 3D Structure Click here
A0A3P7DM63 View 3D Structure Click here
A0A3Q0KJS7 View 3D Structure Click here
A0A3Q0KPU4 View 3D Structure Click here
A0A5K4F604 View 3D Structure Click here
A0A5K4F9V1 View 3D Structure Click here
A0B632 View 3D Structure Click here
A0KKP5 View 3D Structure Click here
A0L4K0 View 3D Structure Click here
A0LFC6 View 3D Structure Click here
A0PZN8 View 3D Structure Click here
A1A1X6 View 3D Structure Click here
A1ARE1 View 3D Structure Click here
A1AWT1 View 3D Structure Click here
A1B4B8 View 3D Structure Click here
A1BJB6 View 3D Structure Click here
A1K4E5 View 3D Structure Click here
A1S702 View 3D Structure Click here
A1TAB5 View 3D Structure Click here
A1TR35 View 3D Structure Click here