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 [1,2]. 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) [3].

1: Genes in the accessory sec locus of Streptococcus gordonii have three functionally distinct effects on the expression of the platelet-binding protein GspB. Takamatsu D, Bensing BA, Sullam PM; Mol Microbiol. 2004;52:189-203. PMID:15049820

2: Asp2 and Asp3 interact directly with GspB, the export substrate of the Streptococcus gordonii accessory Sec System. Yen YT, Seepersaud R, Bensing BA, Sullam PM; J Bacteriol. 2011;193:3165-3174. PMID:21531800

3: Structural and functional insights into the Asp1/2/3 complex mediated secretion of pneumococcal serine-rich repeat protein PsrP. Guo C, Feng Z, Zuo G, Jiang YL, Zhou CZ, Chen Y, Hou WT; Biochem Biophys Res Commun. 2020;524:784-790. PMID:32037091