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0  structures 1105  species 0  interactions 1282  sequences 12  architectures

Family: BBP2_2 (PF10082)

Summary: Putative beta-barrel porin 2

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

This is the Wikipedia entry entitled "Domain of unknown function". More...

Domain of unknown function Edit Wikipedia article

A domain of unknown function (DUF) is a protein domain that has no characterised function. These families have been collected together in the Pfam database using the prefix DUF followed by a number, with examples being DUF2992 and DUF1220. There are now over 3,000 DUF families within the Pfam database representing over 20% of known families.[1]

History

The DUF naming scheme was introduced by Chris Ponting, through the addition of DUF1 and DUF2 to the SMART database.[2] These two domains were found to be widely distributed in bacterial signaling proteins. Subsequently, the functions of these domains were identified and they have since been renamed as the GGDEF domain and EAL domain respectively.

Structure

Structural genomics programmes have attempted to understand the function of DUFs through structure determination. The structures of over 250 DUF families have been solved.[3] This work showed that about two thirds of DUF families had a structure similar to a previously solved one and therefore likely to be divergent members of existing protein superfamilies, whereas about one third possessed a novel protein fold.

Frequency and conservation

Protein domains and DUFs in different domains of life. Left: Annotated domains. Right: domains of unknown function. Not all overlaps shown.[4]

More than 20% of all protein domains were annotated as DUFs in 2013. About 2,700 DUFs are found in bacteria compared with just over 1,500 in eukaryotes. Over 800 DUFs are shared between bacteria and eukaryotes, and about 300 of these are also present in archaea. A total of 2,786 bacterial Pfam domains even occur in animals, including 320 DUFs.[4]

Role in biology

Many DUFs are highly conserved, indicating an important role in biology. However, many such DUFs are not essential, hence their biological role often remains unknown. For instance, DUF143 is present in most bacteria and eukaryotic genomes.[5] However, when it was deleted in Escherichia coli no obvious phenotype was obvious. Later it was shown that the proteins that contain DUF143, are ribosomal silencing factors that block the assembly of the two ribosomal subunits.[5] While this function is not essential, it helps the cells to adapt to low nutrient conditions by shutting down protein biosynthesis. As a result, these proteins and the DUF only becomes relevant when the cells starve.[5] It is thus believed that many DUFs (or proteins of unknown function, PUFs) are only required under certain conditions.

Essential DUFs (eDUFs)

Goodacre et al. identified 238 DUFs in 355 essential proteins (in 16 model bacterial species), most of which represent single-domain proteins, clearly establishing the biological essentiality of DUFs. These DUFs are called "essential DUFs" or eDUFs.[4]

External links

References

  1. ^ Bateman A, Coggill P, Finn RD (October 2010). "DUFs: families in search of function". Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 66 (Pt 10): 1148–52. doi:10.1107/S1744309110001685. PMC 2954198. PMID 20944204. 
  2. ^ Schultz J, Milpetz F, Bork P, Ponting CP (May 1998). "SMART, a simple modular architecture research tool: identification of signaling domains". Proc. Natl. Acad. Sci. U.S.A. 95 (11): 5857–64. doi:10.1073/pnas.95.11.5857. PMC 34487. PMID 9600884. 
  3. ^ Jaroszewski L, Li Z, Krishna SS et al. (September 2009). "Exploration of uncharted regions of the protein universe". PLoS Biol. 7 (9): e1000205. doi:10.1371/journal.pbio.1000205. PMC 2744874. PMID 19787035. 
  4. ^ a b c Goodacre, N. F.; Gerloff, D. L.; Uetz, P. (2013). "Protein Domains of Unknown Function Are Essential in Bacteria". MBio 5 (1): e00744–e00713. doi:10.1128/mBio.00744-13. PMID 24381303.  edit
  5. ^ a b c Häuser, R.; Pech, M.; Kijek, J.; Yamamoto, H.; Titz, B. R.; Naeve, F.; Tovchigrechko, A.; Yamamoto, K.; Szaflarski, W.; Takeuchi, N.; Stellberger, T.; Diefenbacher, M. E.; Nierhaus, K. H.; Uetz, P. (2012). Hughes, Diarmaid, ed. "RsfA (YbeB) Proteins Are Conserved Ribosomal Silencing Factors". PLoS Genetics 8 (7): e1002815. doi:10.1371/journal.pgen.1002815. PMC 3400551. PMID 22829778.  edit

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

This is the Wikipedia entry entitled "Porin (protein)". More...

Porin (protein) Edit Wikipedia article

A single monomer of the same protein in side view, illustrating the antiparallel beta barrel structure.

Porins are beta barrel proteins that cross a cellular membrane and act as a pore through which molecules can diffuse.[1] Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules. They are present in the outer membrane of Gram-negative bacteria and some Gram-positive bacteria of the group Mycolata (mycolic acid-containing actinomycetes), the mitochondria, and the chloroplast.

Structure

Porins are composed of β strands, which are, in general, linked together by beta turns on the cytoplasmic side and long loops of amino acids on the other. The β strands lie in an antiparallel fashion and form a cylindrical tube, called a β barrel.[2] The amino acid composition of the porin β strands are unique in that polar and nonpolar residues alternate along them. This means that the nonpolar residues face outward so as to interact with the nonpolar lipid membrane, whereas the polar residues face inwards into the center of the beta barrel to interact with the aqueous channel. The phospholipids that compose the outer membrane give it the same semi-permeable characteristics as the cytoplasmic membrane.[citation needed]

The porin channel is partially blocked by a loop, called the eyelet, which projects into the cavity. In general, it is found between strands 5 and 6 of each barrel, and it defines the size of solute that can traverse the channel. It is lined almost exclusively with charged amino acids arranged on opposite sides of the channel, creating a transversal electric field across the pore. The eyelet has a local surplus of negative charges from four glutamic acid and seven aspartic acid residues (in contrast to one histidine, two lysine and three arginine residues) is partially compensated for by two bound calcium atoms, and this asymmetric arrangement of molecules is thought to have an influence in the selection of molecules that can pass through the channel.[3]

Cellular roles

To transport medium-sized or charged molecules across, the molecules move through a porin, a water-filled channel or pore.[citation needed]

Porins typically control the diffusion of small metabolites like sugars, ions, and amino acids.

In gram-negative bacteria, the inner membrane is the major permeability barrier, whereas the outer membrane contains porins, which render it largely permeable to molecules less than about 1500 daltons.

The term "nucleoporin" refers to porins facilitating transport through nuclear pores in the nuclear envelope. However, they are often considered distinct from other porins (they are not classified as porins in MeSH.)

Porins are chemically selective – transport only one group of molecules, or may be specific for one molecule[citation needed]. Beta-lactam and fluoroquinolone antibiotics must pass through porins to reach their targets in gram negative bacteria[citation needed]. Bacteria can develop resistance to these antibiotics by mutating the gene that encodes the porin – the antibiotics are then excluded from passing through the outer membrane[citation needed].

Discoverer

The discovery of porins has been attributed to Hiroshi Nikaido, nicknamed "the porinologist."[4]

See also

References

  1. ^ Porins at the US National Library of Medicine Medical Subject Headings (MeSH)
  2. ^ Schirmer T (1998). "General and specific porins from bacterial outer membranes". J. Struct. Biol. 121 (2): 101–9. doi:10.1006/jsbi.1997.3946. PMID 9615433. 
  3. ^ Branden and Tooze, Introduction to Protein Structure, second edition
  4. ^ Klebba PE (December 2005). "The porinologist". J. Bacteriol. 187 (24): 8232–6. doi:10.1128/JB.187.24.8232-8236.2005. PMC 1317029. PMID 16321927. 

External links

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.

Putative beta-barrel porin 2 Provide feedback

This domain is a putative beta-barrel porin type 2.

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR018759

This domain has no known function.

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 MBB (CL0193), which has the following description:

This clan gathers together a large set of beta barrel membrane proteins.Although these proteins have different numbers of beta strands in the barrel they have significant sequence similarity between families.

The clan contains the following 59 members:

Ail_Lom Autotransporter Bac_surface_Ag BBP2 BBP2_2 Campylo_MOMP Channel_Tsx CopB DUF2490 DUF2860 DUF3078 DUF3138 DUF3187 DUF3308 DUF3575 DUF481 DUF560 Gcw_chp HP_OMP HP_OMP_2 KdgM LamB Legionella_OMP MipA MtrB_PioB Omp_AT OMP_b-brl OMP_b-brl_2 OMP_b-brl_3 OmpA_like OmpA_membrane Omptin OmpW Opacity OpcA OprB OprD OprF OstA_C PagL PagP Phenol_MetA_deg Porin_1 Porin_10 Porin_2 Porin_4 Porin_7 Porin_8 Porin_O_P Porin_OmpG ShlB Surface_Ag_2 TcfC Toluene_X TonB_dep_Rec TraF_2 TSA Usher YfaZ

Alignments

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 using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics 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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(1401)
Meta
(51)
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RP35
(139)
RP55
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RP75
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  Seed
(39)
Full
(1282)
Representative proteomes NCBI
(1401)
Meta
(51)
RP15
(55)
RP35
(139)
RP55
(201)
RP75
(259)
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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.

  Seed
(39)
Full
(1282)
Representative proteomes NCBI
(1401)
Meta
(51)
RP15
(55)
RP35
(139)
RP55
(201)
RP75
(259)
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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER3.

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...

Trees

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: COGs (COG5338)
Previous IDs: DUF2320;
Type: Family
Author: COGs, Finn RD, Sammut SJ
Number in seed: 39
Number in full: 1282
Average length of the domain: 335.40 aa
Average identity of full alignment: 21 %
Average coverage of the sequence by the domain: 75.34 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 23.7 23.7
Trusted cut-off 23.7 23.7
Noise cut-off 23.6 23.6
Model length: 381
Family (HMM) version: 5
Download: download the raw HMM for this family

Species distribution

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