The eubacterial secY protein [1] plays an important role in protein export. Itinteracts with the signal sequences of secretory proteins as well as with twoother components of the protein translocation system: secA and secE. SecY isan integral plasma membrane protein of 419 to 492 amino acid residues thatapparently contains ten transmembrane segments. Such a structure probablyconfers to secY a 'translocator' function, providing a channel for periplasmicand outer-membrane precursor proteins.

Homologues of secY are found in archaebacteria [2]. SecY is also encoded inthe chloroplast genome of some algae [3] where it could be involved in aprokaryotic-like protein export system across the two membranes of thechloroplast endoplasmic reticulum (CER) which is present in chromophyte andcryptophyte algae.

In eukaryotes, the evolutionary related protein sec61-alpha plays a role inprotein translocation through the endoplasmic reticulum; it is part of atrimeric complex that also consist of sec61-beta and gamma [4].

This entry represents two conserved sites for secY. The firstcorresponds to the second transmembrane region, which is the most conservedsection of these proteins. The second spans the C-terminal part of the fourthtransmembrane region, a short intracellular loop, and the N-terminal part ofthe fifth transmembrane region.

1. SecY and integral membrane components of the Escherichia coli protein translocation system. Mol. Microbiol. 6, 2423-8
2. Presence of a gene in the archaebacterium Methanococcus vannielii homologous to secY of eubacteria. Biochimie 73, 683-8
3. A secY homologue is found in the plastid genome of Cryptomonas phi. FEBS Lett. 298, 93-6
4. Evolutionary conservation of components of the protein translocation complex. Nature 367, 654-7

The eubacterial secY protein [1] plays an important role in protein e
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