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* Sodium:neurotransmitter symporter family signatures *
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After their release by synapses the action  of  a  number of neurotransmitters
is  terminated  by  their   high  affinity   sodium-dependent   reuptake  into
presynaptic terminals  by specific transport proteins [1 to 4]. These proteins
are the  target of psychomotor stimulants such as amphetamines or cocaine. All
these proteins  belong  to  a family, known [5] as the sodium:neurotransmitter
symporter family  (SNF),  that  also  include  some transporters that function
outside the  brain  and  carry  related molecules. The SNF family is currently
known to consist of transporters for:

 - Betaine (also transports GABA).
 - Choline.
 - Creatine.
 - Dopamine.
 - GABA (four different forms of GABA transporters have been characterized).
 - Glycine.
 - Noradrenaline.
 - Proline.
 - Serotonin (5HT).
 - Taurine.

 - Rat orphan transporter NTT4.
 - Caenorhabditis elegans hypothetical transporter T23G5.5.

All these  transporters  are  glycoproteins  of  about  600  to 700 amino acid
residues which  seem  to  contain  12  transmembrane  domains. Apparently both
termini are cytoplasmically located.

As signature patterns for these proteins we have selected two highly conserved
regions. The first region spans the C-terminal part of the first transmembrane
domain, a short extracellular  loop,   and  the N-terminal part of  the second
transmembrane  domain.   The  second  region   is   located  in   the  largest
extracellular loop between the third  and fourth  transmembrane domains;  this
region  contains two conserved cysteines  that  could be involved in disulfide
bonds.

-Consensus pattern: W-R-F-P-Y-x-[CA]-x(2)-N-G-G-G-x-[FY]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: Y-[LIVMFY]-x(2)-[SC]-[LIVMFY]-[STQ]-x(2)-L-P-W-x(2)-C-
                    x(4)-N-[GST]
                    [The C could be involved in a disulfide bond]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: June 1994 / Patterns and text revised.

[ 1] Snyder S.H.
     Nature 354:187-187(1991).
[ 2] Schloss P., Mayser W., Betz H.
     FEBS Lett. 307:76-80(1992).
[ 3] Attwell D., Bouvier M.
     Curr. Biol. 2:541-543(1992).
[ 4] Uhl G.R.
     Trends Neurosci. 15:265-268(1992).
[ 5] Reizer J., Reizer A., Saier M.H. Jr.
     Submitted(1993).