Signal peptidase

Peptidase_S26
Identifiers
Symbol Peptidase_S26
Pfam PF10502
Pfam clan CL0299
InterPro IPR019533
MEROPS S26
OPM superfamily 137
OPM protein 1t7d
Membranome 323
Signal peptidase complex subunit 3
Identifiers
Symbol SP3
Pfam PF04573
InterPro IPR007653
Membranome 369
Signal peptidase I
Identifiers
EC number 3.4.21.89
CAS number 65979-36-4
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO
Signal peptidase II
Identifiers
EC number 3.4.23.36
CAS number 171715-14-3
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO

Signal peptidases are enzymes that convert secretory and some membrane proteins to their mature forms by cleaving their signal peptides from their N-terminals.

Signal peptidases were initially observed in endoplasmic reticulum (ER)-derived membrane fractions isolated from mouse myeloma cells.[1] The key observation by César Milstein and colleagues was that immunoglobulin light chains were produced in a higher molecular weight form, which became processed by the ER membrane fraction. This finding was directly followed by the discovery of the translocation machinery.[2] Signal peptidases are also found in prokaryotes as well as the protein import machinery of mitochondria and chloroplasts.[3]

All signal peptidases described so far are serine proteases. The active site that endoproteolytically cleaves signal peptides from translocated precursor proteins is located at the extracytoplasmic site of the membrane. The eukaryotic signal peptidase is an integral membrane protein complex. The first subunit, which was identified by yeast genetics is Sec11, a 17 kDa membrane protein that is associated with three subunits termed Spc3p (21 kDa), Spc2p (18 kDa) and Spc1p (11 kDa). Sec11 is the only essential factor for signal peptide processing as can be deduced from a growth defect upon its deletion.[4] The functional signal peptidase complex was first purified from a canine ER membrane fraction.[5] The five mammalian subunits are named SPC12, SPC18, SPC21, SPC22/23 and SPC25 according to their molecular weight.

References

  1. ↑ Milstein C, Brownlee GG, Harrison TM, Mathews MB (September 1972). "A possible precursor of immunoglobulin light chains". Nature New Biology. 239 (91): 117–20. doi:10.1038/newbio239117a0. PMID 4507519.
  2. ↑ Blobel G, Dobberstein B (December 1975). "Transfer of proteins across membranes. I. Presence of proteolytically processed and unprocessed nascent immunoglobulin light chains on membrane-bound ribosomes of murine myeloma". J. Cell Biol. 67 (3): 835–51. doi:10.1083/jcb.67.3.835. PMC 2111658. PMID 811671.
  3. ↑ Paetzel M, Karla A, Strynadka NC, Dalbey RE (December 2002). "Signal peptidases". Chem. Rev. 102 (12): 4549–80. doi:10.1021/cr010166y. PMID 12475201.
  4. ↑ Böhni PC, Deshaies RJ, Schekman RW (April 1988). "SEC11 is required for signal peptide processing and yeast cell growth". J. Cell Biol. 106 (4): 1035–42. doi:10.1083/jcb.106.4.1035. PMC 2115025. PMID 3283143.
  5. ↑ Evans EA, Gilmore R, Blobel G (February 1986). "Purification of microsomal signal peptidase as a complex". Proc. Natl. Acad. Sci. U.S.A. 83 (3): 581–5. doi:10.1073/pnas.83.3.581. PMC 322907. PMID 3511473.
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