Asp2 is a family of the SecA2/Y2 accessory Sec secretory system of Gram-positive bacteria. It is specific for large serine-rich repeat, cell-wall-anchored, glycoproteins such as GspB. Export of GspB requires the three Asp1-Asp3 proteins. Asp2, in conjunction with Asp3, probably acts as a chaperone in the early stage of GspB transport. Asp2 directly interacts with Aps1 and Asp3 to form a complex and stabilizes it; this complex is essential for substrate export. Moreover, Asp2 acetylates the GlcNAc residues on GspB. Asp1/2/3 complex stimulates the ATPase activity of SecA2 and also affects the export and glycosylation of pneumococcal serine-rich repeat proteins (PrsPs).
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