Table 3.
Characteristics of signal peptidases and target signal peptides
| Model Signal Peptidase | Example Protein | Merops Family & domains | Translocation system | Signal peptide domain | Example substrates | Domains | Comments |
|---|---|---|---|---|---|---|---|
| N-terminal Processing | |||||||
| PilD PulO GspO | SO_0414 | A24A | T2aSS | pfam07963 | GspGHIJK | pfam02501 pfam03934 pfam08334 pfam12019 | Signal peptides similar, except ones in IVb pili are longer (~25 aa) than others (~7 aa), GspK, PilX, PilW are not detected by pfam07963 |
| T2bSS | type IVa pili | ||||||
| type IVb pili | |||||||
| TadV | Spea_2010 | A24A | T2cSS | Flp, TadEF | |||
| LspA | SO_3531 | A08 pfam01252 |
Sec | Lipo-proteins | |||
| Tat | TIGR01409 pfam10518 | ||||||
| NA1 | SO_A0049 | C39 | T1SS | TIGR01847 | class Ia & IIa-b bacteriocin, microcins | pfam01721 pfam10439 pfam10439 | The signal peptidase activity is encoded in the permease component of the T1SS system that exports the bacteriocin |
| LepB | SO_1347 | S26A pfam00717 |
Sec | exported proteins | |||
| Tat | TIGR01409 pfam10518 | ||||||
| C-terminal processing | |||||||
| ? | T4bSS - IncF | TraA | mature TraA is about ~68 aa in length with two TM spans that circularizes | ||||
| TrhF | Shewana3_4209 | S26A | T4bSS - IncH | TrhA HdtZ | Substrates have Sec signal peptide that is cleaved by LepB | ||
| TraF | Sputw3181_1142 | S26A | T4bSS - IncJ | TraA | TIGR02758 | ||
| TraF | Shewana3_1267 | S26C pfam00717 |
T4bSS - IncP | TrbC | pfam04956 | ||