While most of what Olivier and Vincent say is right, I have two slight corrections:
1) The active zone (AZ) is not just a specialised part of the presynaptic membrane - it extends into the cytoplasm of the presynaptic terminal for several µm. There is a highly organised and densely packed protein assembly, called the cytomatrix at the active zone (CAZ), which is a defining part of the AZ. The CAZ contains many scaffolding proteins, like bassoon, piccolo, RIM 1, and Munc13, which help to keep channels in place and prepare synaptic vesicles for fusion.
2) Syntaxin 1 and SNAP25 are essential for the release of synaptic vesicles, but they are not necessarily specialised AZ proteins. Rather, they seem to coat the entire presynaptic membrane, regardless of whether there is an AZ nearby or not (Wilhelm et al., Science, 2014). For syntaxin 1, there is even a significant proportion on synaptic vesicles (Takamori et al., Cell, 2006).
The active zone has specialized anchoring proteins to allow vesicles to fuse.
Synaptotagmin, synaptotagmin, SNARE proteins, etc..
Presynaptic membrane just refers to any old presynaptic part that could be close to a synapse but without special docking machinery.
Thanks. Channels and transporters are located in the presynaptic membrane. Does it mean that the active zone is just part of the presynaptic membrane?
Yes, the active zone is a part of the presynaptic membrane. What makes it the "active zone" is simply the presence of specialized proteins that allows presynaptic vesicles to dock, fuse, and, ultimately, release neurotransmitter into the synaptic cleft (as said by Thibault). However, synaptotagmin is not a protein found in the active zone (it's a calcium sensor found on the presynaptic vesicle membrane). Syntaxin and SNAP25 are examples of specialized active zone proteins.
While most of what Olivier and Vincent say is right, I have two slight corrections:
1) The active zone (AZ) is not just a specialised part of the presynaptic membrane - it extends into the cytoplasm of the presynaptic terminal for several µm. There is a highly organised and densely packed protein assembly, called the cytomatrix at the active zone (CAZ), which is a defining part of the AZ. The CAZ contains many scaffolding proteins, like bassoon, piccolo, RIM 1, and Munc13, which help to keep channels in place and prepare synaptic vesicles for fusion.
2) Syntaxin 1 and SNAP25 are essential for the release of synaptic vesicles, but they are not necessarily specialised AZ proteins. Rather, they seem to coat the entire presynaptic membrane, regardless of whether there is an AZ nearby or not (Wilhelm et al., Science, 2014). For syntaxin 1, there is even a significant proportion on synaptic vesicles (Takamori et al., Cell, 2006).
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