SctA is an MLB-associated protein.

<p>Immunofluorescence analyses using the anti-SctA antibody on (<b>A</b>) axenic cells, (<b>B</b>) cells grown with bacteria, and (<b>C</b>) purified MLBs. The cell cultures and purified material were deposited on glass slides. Nuclei or bacterial DNA were stained with DAPI, actin was stained with fluorescent phalloidin, and the cells were labeled using the anti-SctA antibody and a peroxidase-conjugated secondary antibody. In axenic conditions, SctA was observed in dot-like structures within the cells and on secreted pycnosomes. In the presence of bacteria (not visible on the photograph), SctA was found on extracellular MLBs, which are larger structures than pycnosomes. Some of the MLBs did not appear to be SctA-positive. Purified MLBs were all labeled with the anti-SctA antibody but the intensity of fluorescence was uneven. The arrows indicate MLBs and pycnosomes. (<b>D)</b> Western blot analysis with the anti-SctA antibody. The protein was detected in ~10 and 18-kDa bands in the MLB sample and in 10 and 17-kDa bands in the cell lysate (500,000 axenically grown cells). The purified MLB and cell lysate samples contained 5% 2-mercaptoethanol and denaturation solution. Scale bar: A to C = 5 μm.