G3DSA:1.10.3370.10

SecY subunit domain

CATH-Gene3D entry
Member databaseCATH-Gene3D
CATH-Gene3D typehomologous superfamily

Description
Imported from IPR023201

Secretion across the inner membrane in some Gram-negative bacteria occurs via the preprotein translocase pathway. Proteins are produced in the cytoplasm as precursors, and require a chaperone subunit to direct them to the translocase component
[2]
. From there, the mature proteins are either targeted to the outer membrane, or remain as periplasmic proteins. The translocase protein subunits are encoded on the bacterial chromosome.

The translocase itself comprises 7 proteins, including a chaperone protein (SecB), an ATPase (SecA), an integral membrane complex (SecY, SecE and SecG), and two additional membrane proteins that promote the release of the mature peptide into the periplasm (SecD and SecF)
[2]
. The chaperone protein SecB
[1]
is a highly acidic homotetrameric protein that exists as a "dimer of dimers" in the bacterial cytoplasm. SecB maintains preproteins in an unfolded state after translation, and targets these to the peripheral membrane protein ATPase SecA for secretion
[3]
. The structure of the Escherichia coli SecYEG assembly revealed a sandwich of two membranes interacting through the extensive cytoplasmic domains
[5]
. Each membrane is composed of dimers of SecYEG. The monomeric complex contains 15 transmembrane helices.

This superfamily represents the structural domain of SecY
[4]
.

References
Imported from IPR023201

1.SecB, a molecular chaperone with two faces. Driessen AJ. Trends Microbiol. 9, 193-6, (2001). View articlePMID: 11336818

2.The sec and prl genes of Escherichia coli. Bieker KL, Phillips GJ, Silhavy TJ. J. Bioenerg. Biomembr. 22, 291-310, (1990). View articlePMID: 2202721

3.Effects of pre-protein overexpression on SecB synthesis in Escherichia coli. Muller JP. FEMS Microbiol. Lett. 176, 219-27, (1999). PMID: 10418149

4.X-ray structure of a protein-conducting channel. Van den Berg B, Clemons WM Jr, Collinson I, Modis Y, Hartmann E, Harrison SC, Rapoport TA. Nature 427, 36-44, (2004). View articlePMID: 14661030

5.Three-dimensional structure of the bacterial protein-translocation complex SecYEG. Breyton C, Haase W, Rapoport TA, Kuhlbrandt W, Collinson I. Nature 418, 662-5, (2002). View articlePMID: 12167867

Further reading

6. A secY homologue is found in the plastid genome of Cryptomonas phi. Douglas SE. FEBS Lett. 298, 93-6, (1992). View articlePMID: 1544427

7. Isolation of a secY homologue from Bacillus subtilis: evidence for a common protein export pathway in eubacteria. Suh JW, Boylan SA, Thomas SM, Dolan KM, Oliver DB, Price CW. Mol. Microbiol. 4, 305-14, (1990). View articlePMID: 2110998

8. SecY and integral membrane components of the Escherichia coli protein translocation system. Ito K. Mol. Microbiol. 6, 2423-8, (1992). PMID: 1406280

9. Presence of a gene in the archaebacterium Methanococcus vannielii homologous to secY of eubacteria. Auer J, Spicker G, Bock A. Biochimie 73, 683-8, (1991). View articlePMID: 1764515

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