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151  structures 2120  species 0  interactions 5663  sequences 230  architectures

Family: BNR_2 (PF13088)

Summary: BNR repeat-like domain

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This is the Wikipedia entry entitled "Bacterial neuraminidase". More...

Bacterial neuraminidase Edit Wikipedia article

BNR/Asp-box repeat
PDB 1euu EBI.jpg
Structure of a bacterial sialidase.[1]
Pfam clanCL0434

Bacterial neuraminidase is type of neuraminidase and a virulence factor for many bacteria including Bacteroides fragilis and Pseudomonas aeruginosa. Its function is to cleave a sialic acid residue off ganglioside-GM1 (a modulator of cell surface and receptor activity) turning it into asialo-GM1 to which type 4 pilli (attachment factors) bind preferentially.


  1. ^ Gaskell A, Crennell S, Taylor G (November 1995). "The three domains of a bacterial sialidase: a beta-propeller, an immunoglobulin module and a galactose-binding jelly-roll". Structure. 3 (11): 1197–205. doi:10.1016/s0969-2126(01)00255-6. PMID 8591030.

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

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.

BNR repeat-like domain Provide feedback

This family of proteins contains BNR-like repeats suggesting these proteins may act as sialidases.

Internal database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR011040

Sialidases (neuraminidases) hydrolyse the non-reducing, terminal sialic acid linkage in various natural substrates, such as glycoproteins, glycolipids, gangliosides, and polysaccharides [ PUBMED:12374200 ]. In mammals, sialidases occur in the lysosome, the cytosol, and associated with the plasma membrane. Sialidases have also been implicated in the pathogenesis of many diseases. For example, in viruses neuraminidases enable the transport of the virus through mucin, the eruption of the virus from the infected host cell, and the prevention of self-aggregation of virus particles through the destruction of the host cell receptor recognised by the virus [ PUBMED:14561719 ]. Eukaryotic, bacterial and viral sialidases share highly conserved regions of beta-sheet motifs. Bacterial sialidases often possess domains in addition to the catalytic sialidase domain, for instance the sialidase from Micromonospora viridifaciens contains three domains, of which the catalytic domain described here is the N-terminal domain [ PUBMED:8591030 ]. Similarly, leech sialidase is a multidomain protein, where the catalytic domain is the C-terminal domain [ PUBMED:9878409 ]. In several paramyxoviruses, sialidase forms part of the multi-functional haemagglutinin-sialidase glycoprotein found on the viral envelope [ PUBMED:14729348 ].

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 Sialidase (CL0434), which has the following description:

This superfamily includes sialidases enzymes. Several viruses use sialic acid as a cell surface receptor for host invasion. These viruses then have cell surface neuraminidase enzymes to cleave sialic acid from cell surface proteins allowing them to leave the host cell after replication. This superfamily are composed of six beta-sheets that form a six-fold beta-propeller structure. Many members of this superfamily contain BNR sequence motifs Pfam:PF02012.

The clan contains the following 16 members:

BNR BNR_2 BNR_3 BNR_4 BNR_6 End_beta_barrel End_beta_propel Fungal_lectin HN Mcl1_mid Neur Neuraminidase OLF Phytase PSII_BNR Sortilin-Vps10


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.

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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.

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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: Jackhmmer:O25303
Previous IDs: none
Type: Repeat
Sequence Ontology: SO:0001068
Author: Bateman A
Number in seed: 36
Number in full: 5663
Average length of the domain: 273.30 aa
Average identity of full alignment: 19 %
Average coverage of the sequence by the domain: 58.31 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 31.4 31.4
Trusted cut-off 31.4 31.4
Noise cut-off 31.3 31.3
Model length: 278
Family (HMM) version: 8
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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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 BNR_2 domain has been found. There are 151 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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