Outer membrane protein in the supernatant!? - (Mar/28/2006 )

Does anyone knows if an outer membrane protein can be found in the supernatant?

outer membrane...
I know that Streptococcus ( OKay, it's a gram positive) has a protein from the cell wall that can be cleaved and released in the supernatant.

I have no particular example for a gram negative....
some one knows?