Improving protein secretion by engineering components of the bacterial translocation machinery

The increased insight into the mechanism of bacterial protein translocation has resulted in new concepts for the production of heterologous proteins. The periplasm of Gram-negative bacteria is revealed to have a role as a 'pr otein construction compartment', which can be used to fold complex proteins . Passage across the outer membrane, however, remains a challenge due to th e high selectivity of the outer membrane translocase. In Gram-positive bact eria, slow folding at the membrane-cell-wall interface can make heterologou s proteins vulnerable to degradation by wall-associated proteases. The rece nt identification of thiol-disulfide oxidoreductases in Bacillus subtilis m ight open the possibility of secreting proteins containing multiple disulfi de bonds from this host.