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Weapons Delivery and Deployment. Protein secretion in bacteria. Membranes act as a barrier to the movement of large molecules into or out of the cell Gram-positive and Gram-negative bacteria have many important structures which are located outside the wall
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Protein secretion in bacteria • Membranes act as a barrier to the movement of large molecules into or out of the cell • Gram-positive and Gram-negative bacteria have many important structures which are located outside the wall • So how are the large molecules from which some of these structures are made transported out of the cell for the assembly? • How about exoenzymes and other proteins? How are they released through the membrane? • Mechanisms of protein secretion are important and can be exploited for vaccine development.
y • Different cell layers for Gram + and Gram – bacteria • For Gram +, the secreted proteins must be transported across a single membrane. Then through a relatively porous peptidoglycan into either: • the external environment • become embedded /attached to the peptidoglycan • For Gram –, the secreted protein must be transported across the IM; escape protein-degrading enzymes in the periplasmic space; and finally across the OM
Sec-dependent pathway • Secretion-dependent • a.k.a general secretion pathway • Require energy from hydrolysis of ATP or GTP, and sometimes by proton motive force • Preprotein with signal peptide, chaperone protein
