Signal peptide - periplasmic protein - (Mar/03/2005 )
I may have found a periplasmic protein in a G- bacterium. We are pretty sure of its localization by more than one experiment (and more than one paper published by other research groups).
However, its aa sequence does not have a signal peptide.
How this is possible?
maybe your protein does not have a signal peptide because it have an interaction with a protein carrier which get itself the signal peptide.
I'm not sure but maybe the peptide signal is clived in a maturation process which occurs after the fixation in the membrane (but this idea is less possible cause the signal would exist in the gene). The sequence you mentioned above is maybe the mature one?
How did you deduce the sequence of the protein. from the DNA sequence by peptide sequencing.
If you have used the protein extracte from the perilasm them, you will have see a signal peptide, as duirng the transmembrane transport the signal peptide is cleaved off.