Family A24
Summary for family A24
| Name | Peptidase family A24 (type IV prepilin peptidase family) |
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| Family type peptidase | A24.001 - type 4 prepilin peptidase 1 (Pseudomonas aeruginosa), MEROPS Accession MER0000870 (peptidase unit: 50-281) |
| Content of family | Peptidase family A24 contains membrane-inserted endopeptidases. |
| History |
Identifier created: MEROPS 5.00 (20 April 2000)
The catalytic mechanism of the bacterial peptidase that processes type 4 prepilin (A24.001) has long been a puzzle, but it now seems that it is an aspartic peptidase. The archaean preflagellin peptidase (A24.016) is a distant homologue. |
| Catalytic type | Aspartic |
| Active site | The active site residues of the peptidases of family A24 are both aspartates (LaPointe & Taylor, 2000). In subfamily A24A, the two active-site Asp residues occur in the motifs Xaa-Xaa-Asp-Xaa-Xbb-Xcc-Xcc-Xcc-Xaa-Pro and Xaa-Gly-Xcc-Gly-Asp-Xaa-Lys-Xaa-Xaa-Xaa (where Xaa is hydrophobic, Xbb is charged and Xcc is any amino acid) (Rawlings & Barrett, 2004) (see the Alignment). |
| Activities and specificities | The prepilin peptidases (A24.001, A24.003) process type 4 pilin precursor proteins (prepilins) to their mature forms by removal of leader peptides. The leader peptides differ from those processed by signal peptidase I (S26.001) in that they are 5 - 8 residues long, rich in acidic amino acids, and immediately precede a 20-residue hydrophobic region. The consensus sequence of the cleavage site is Gly Phe.
Also in the family is preflagellin peptidase (A24.016). Some archaea possess a flagellum different from those found in bacteria that contain a flagellin protein that is synthesized as a precursor with a positively charged leader peptide; the leader peptide is removed by the preflagellin peptidase before the protein is incorporated into the filament (Bardy & Jarrel, 2002). |
| Molecular structure | The tertiary structure of the preflagellin peptidase from Methanococcus maripaludis has been solved, and shows a bundle of six transmembrane helices. The active site aspartates are on helices 1 and 4, and are far apart, implying that a conformational change is required to activate the peptidase (Hu et al., 2011). The structure is unique to family A24, and is the type structure for clan AD. The peptidases of subfamily A24A contain eight predicted transmembrane domains (five of which are included in the peptidase unit: see the Alignment). |
| Clan | AD |
| Basis of clan assignment | Type family of clan AD. |
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Peptidases not assigned to subfamily
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