The central subunit of a protein translocation channel (Potential). Part of the accessory SecA2/SecY2 system specifically required to export GspB, a serine-rich repeat cell wall protein encoded upstream in the same operon. May form heterotrimers with SecE and SecG subunits (Potential). Component of the accessory SecA2/SecY2 protein translocase complex required to export cell wall protein GspB. Loss of adherence to human platelet cells, loss of export of cell wall protein GspB; GspB accumulates in the cytoplasm. Belongs to the SecY/SEC61-alpha family. SecY2 subfamily.