Fig. 8.
The SRR domains of GspB are important for optimal export. Variants of S. gordonii strain M99 expressing glycosylated GspB736FLAG, nonglycosylated GspB736FLAG (NG), or a GspB736FLAG lacking both SRR regions (ΔSRRs) were cultured overnight. Export of each protein from S. gordonii was assessed by comparing levels of GspB secreted into the culture medium (M) or retained in the protoplast (P) by Western blotting with anti-FLAG antibody (blots I and II). The β-subunit of RNA polymerase in the protoplasts (blot III) served as a loading control. For clarity, the GspB variants on blot II are indicated. Note that three proteins of 150, 75, and 70 kDa that cross-react with the anti-FLAG antibody are present in all lanes on this blot.