2.A.1.22.1
Synaptic vesicle glycoprotein neurotransmitter (e.g., dopamine) transporter, SV2A or SLC22B1.  This protein localizes to neurotransmitter-containing vesicles and has a nucleotide binding site (Yao and Bajjalieh 2009). The SV2 family is comprised of three paralogues: SV2A, SV2B, and SV2C. They are present in secretory vesicles, including synaptic vesicles, and are critical to neurotransmission. Structural and functional studies suggest that SV2 proteins may play several roles to promote proper vesicular function. Among these roles are their potential to stabilize the transmitter content of vesicles, to maintain and orient the releasable pool of vesicles, and to regulate vesicular calcium sensitivity to ensure efficient, coordinated release of the transmitter (Stout et al. 2019). SV2A plays a role in neuronal excitability and as such is the specific target for the antiepileptic drug levetiracetam as well as seletracetam and brivaracetam. SV2 proteins also act as the target by which potent neurotoxins, particularly botulinum, gain access to neurons and exert their toxicity. Both SV2B and SV2C are increasingly implicated in diseases such as Alzheimer's disease and Parkinson's disease. Despite decades of intensive research, their exact functions were elusive in 2019 (Stout et al. 2019), but the systems may transport galactose.The human (Q70J3) and rat orthologs are 99% identical. The structure, function, and disease relevance of GP2 (SV2) transporters have been reviewed (Stout et al. 2019).