Family A8
Summary for family A8
| Name | Peptidase family A8 (signal peptidase II family) |
|---|
| Family type peptidase | A08.001 - signal peptidase II (Escherichia coli), MEROPS Accession MER0001313 (peptidase unit: 1-164) |
| Content of family | Peptidase family A8 contains an endopeptidase, the bacterial signal peptidase II. |
| History |
Identifier created: Proteolysis in Cell Function, pp13-21, IOS Press, Amsterdam (1997)
|
| Catalytic type | Aspartic |
| Active site residues | D114 D141 |
| Active site | Two aspartate residues have been shown by site-directed mutagenesis to be essential for activity (Tjalsma et al., 1999). These occur in the motifs GNXXDRX and FNXAD where X is a hydrophobic residue. |
| Activities and specificities | Cleavage of the prelipoprotein occurs on the amino side of a modified cysteine residue, the thiol group of which is substituted with a diacylglyceryl group (an activity of phosphatidylglycerol:prolipoprotein diacylglyceryl transferase). The consensus around the cleavage site is known as the 'lipobox sequence' and is Leu-Xaa-Yaa Cys in which Xaa is Ala or Ser and Yaa is Gly or Ala. The specificity of the peptidase was examined in detail by Gonnet et al. (2004). |
| Inhibitors | The cyclic pentapeptide antibiotic globomycin is a potent noncompetitive inhibitor. Pepstatin, Tos-Arg-OMe and mercuric chloride also inhibit at concentrations below 1 mM (Sankaran, 2004). |
| Molecular structure | Signal peptidase II is membrane bound with four transmembrane domains. The active site is close to the membrane surface between transmembrane domains three and four on the periplasmic side. Although the tertiary structure has not been determined, the fold is unlikely to be similar to that of any other aspartic peptidase and so family A8 is assigned to its own clan, AC. |
| Clan | AC |
| Basis of clan assignment | Type family of clan AC. |
| Biological functions | Signal peptidase II removes the signal peptide from the N-terminus of the murein prolipoprotein, an essential step in the production of the bacterial cell wall. Homologues are known from nearly every bacterial genome so far completely sequenced. A few bacteria, including Pseudomonas fluorescens and Staphylococcus epidermidis, contain two family A8 homologues. |
| Reviews | Sankaran (2004) |
| Statistics for family A8 | Sequences: | 8864 |
| Identifiers: | 1 |
| Identifiers with PDB entries: | 1 |
| Downloadable files |
Sequence library (FastA format) |
| Sequence alignment (FastA format) |
| Phylogenetic tree (Newick format) |
