Table 3 List of general secretory pathways in different organisms
Organism | Secretory pathway | Description |
|---|---|---|
Gram-negative bacteria | Type I secretory pathway | An oligomeric complex composed of an inner membrane ATP-binding cassette exporter, a membrane fusion protein, and an outer membrane homologue. |
| Â | Type II secretory pathway, also known as the general secretory pathway | A two-step process: 1) proteins are moved across the inner membrane through the Sec system, and 2) proteins are moved across the outer membrane. |
| Â | Type III secretory pathway | A highly regulated channel through both the inner and outer membranes forming a needle-like structure. |
| Â | Type IV secretory pathway | Involves conjugative transfer of DNA and nucleoprotein complexes. |
| Â | Type V secretory pathway | A large family of protein-translocating outer membrane porins. |
| Â | Type VI secretory pathway | Forms a transenvelope apparatus. It also exists in plant, animal, and human pathogens, and environmental strains. |
| Â | Type VII secretory pathway | Exists mainly in Mycobacterium and Gram-positive bacteria to a small degree. |
Gram-positive bacteria | Sec-type pathways | Involves Sec-type signal peptides. |
Mammalian cells | Non-vesicular secretory pathway | Type I is a self-sustained protein translocation across plasma membranes. |
| Â | Â | Type II is an ATP-binding cassette transporter-based secretion. |
| Â | Vesicular secretory pathway | Type III is an autophagy-based secretion. |
| Â | Â | Type IV comprises the proteins that bypass the Golgi apparatus to transport to the plasma membrane. |
Eukaryotic cells | Budding from endoplasmic reticulum to form the coat protein complex II (COPII) vesicles | Essential processes are similar from yeasts to higher eukaryotes. |
Archaea | Similar to Sec-type pathways | Most Archaea have a homologue of CsaA. |