The central subunit of the protein translocation channel SecYEG. Consists of two halves formed by TMs 1-5 and 6-10. These two domains form a lateral gate at the front which open onto the bilayer between TMs 2 and 7, and are clamped together by SecE at the back. The channel is closed by both a pore ring composed of hydrophobic SecY resides and a short helix (helix 2A) on the extracellular side of the membrane which forms a plug. The plug probably moves laterally to allow the channel to open. The ring and the pore may move independently. SecY is required to insert newly synthesized SecY into the inner membrane. Overexpression of some hybrid proteins has been thought to jam the protein secretion apparatus resulting in cell death; while this may be true, overexpression also results in FtsH-mediated degradation of SecY. Component of the Sec protein translocase complex. Heterotrimer consisting of SecY, SecE and SecG subunits. The heterotrimers can form oligomers, although 1 heterotrimer is thought to be able to translocate proteins. Interacts with the ribosome. Interacts with SecDF-YajC and YidC; YidC interacts with nascent inner membrane proteins after SecY. The SecDF-YidC-YajC translocase forms a supercomplex with SecYEG, called the holo-translocon (HTL) (PubMed:27435098). The stoichiometry of the super complex may be SecYEG:YidC:SecDF 4:3:1, YajC is in the reconstituted complex (with SecDF) but as no antibody is available it could not be quantified (PubMed:27435098). SecY probably contacts the 23S rRNA and possibly also ribosomal protein L23 during ribosome docking. A single SecY molecule forms the translocating pore, although interaction with SecA may require oligomers. SecY that is not part of the protein translocation apparatus is degraded by FtsH. Also degraded by FtsH when the SecYEG complex is jammed, or upon treatment with antibiotics that block translation elongation such as chloramphenicol. Belongs to the SecY/SEC61-alpha family.