Protein secretion


Microbial proteins being secreted from the cell are very often associated with virulence, degradative processes and the acquisition of nutrients. In gram-negative bacteria, various protein secretion systems have been described. The extracellular enzyme, levansucrase is secreted by a yet-to-be identified process. This enzyme does not possess a signal peptide sequence but nevertheless is found in the periplasmic space. Consequently, none of the well-established protein secretion systems might be relevant for its export and secretion. Using different approaches, our group is in the process of dissecting the appropriate secretion system. Interestingly, two very similar levansucrase isoenzymes, LscB and LscC, accumulate differentially in the periplasm (LscC) and in the extracellular space (LscB). Genes and gene products required for the differential export and secretion of both enzymes are being investigated.