VAT-1 is a major protein from Torpedo synaptic vesicles. A protein data-base search revealed a striking homology to ξ crystallin from guinea pig lens. The overall amino-acid identity is 27%, and 58% similarity is reached by including conserved substitutions. The highest similarity (60% to 85%) between the two proteins is observed in five discrete domains, which are also conserved in zinc-dependent dehydrogenases, particularly in the alcohol dehydrogenase family. The cofactor-binding domain of oxidoreductases is conserved in VAT-1 and in ξ crystallin. VAT-1 preferably binds NADPH in the presence of zinc. In contrast with its homologous proteins, VAT-1 is an integral membrane protein of synaptic vesicles.
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Acknowjledgements: We wish to thank Dr. D.M. Michaelson, Dept. of Neurochemistry, Tel Aviv University, for providing Torpedo tissue and to D. Parnas for critically reading of the manuscript. This work was partially supported by the US-Israel Binational Foundation (Grant 89-00209).
- Electric organ
- Lens crystallin
- Protein evolution
- Synaptic vesicle