Conservation of binding-site residues in NSS proteins
The generic numbers and the residue numbers in LeuT are shown in the first column. The next five columns list the various contacts of the two sodium ions and the leucine substrate, as observed in the LeuT structure. The contact residues for leucine in LeuT were defined as those residues with different solvent-accessible surface areas in the presence and absence of bound substrate. A2.5-Å distance cut-off was used to determine all Na-coordinating residues. Residues from prokaryotic NSS-family members with known substrates (LeuT, TnaT and Tyt1) are shown in the next three columns, and the two columns after that list the variability in 167 prokaryotic NSS-proteins. Residues from eukaryotic NSS-proteins with known substrates are shown in the next 11 columns. These include transporters for DAT, NET, SERT, betaine (BET), GABA (GAT), taurine (TAUT), creatine (CREAT), glycine (GLYT), proline (PROT), neutral amino acids (NAAT), and neutral and cationic amino acids (NCAAT). Finally, the two columns farthest to the right show the variability in 177 eukaryotic NSS proteins. Conserved residues shown in cyan in Figure 8 are indicated in bold. Contact positions classified as conserved were those in all NSS-proteins with known substrate that featured very similar residue types (Ser and Thr, or Asn and Asp, etc.). Position 1.45 (shown in green in Figure 8), is a Gly in all NSS proteins, except in the biogenic amine transporters, where it is an Asp, and is shown in italic. Amino acids are referred to by the one-letter codes.
Generic No. (LeuT No.) | Contacts | Prokaryotic | Eukaryotic | ||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Side Chain | Back bone | Leu | Na1 | Na2 | LeuT | TnaT | Tyt1 | Types | DAT | NET | SERT | BET | GAT | TAUT | CREAT | GLYT | PROT | NAAT | NCAAT | Types | |||||||||||||||||||||||
| 1.41 (20) | √ | √ | G | G | G | G(98%) | 4 | G | G | G | G | G | G | G | G | G | G | G | G(83%), S(11%), A(5%) | 4 | |||||||||||||||||||||||
| 1.42 (21) | √ | √ | bs | N | N | S | S(70%), A(21%) | 8 | F | F | Y/F | E | E/Y/L | G | F | Y | Y | F | Y | Y(38%), F(31%), E(8%), L(7%), G(6%) | 10 | ||||||||||||||||||||||
| 1.43 (22) | √ | b | √ | A | A | A | A(89%), T(8%) | 5 | A | A | A | I | I/A | F | A | A | C | C | A | A(55%), S(21%), I(8%), C(5%) | 8 | ||||||||||||||||||||||
| 1.44 (23) | √ | √ | V | V | V | V(64%), I(34%) | 6 | V | V | V | I | I | V | V | V | V | V | V | V(76%), I(19%) | 5 | |||||||||||||||||||||||
| 1.45 (24) | √ | b | G | G | G | G(99%) | 2 | D | D | D | G | G | G | G | G | G | G | G | G(75%), D(17%) | 5 | |||||||||||||||||||||||
| 1.46 (25) | √ | b | L | L | M | L(81%), F(7%), I(5%) | 7 | L | L | L | L | L | L | L | L | L | L | L | L(94%) | 4 | |||||||||||||||||||||||
| 1.47 (26) | √ | b | G | G | G | G(98%) | 2 | A | A | G | G | G | G | G | G | G | G | G | G(85%), A(9%) | 4 | |||||||||||||||||||||||
| 1.48 (27) | √ | √ | N | N | N | N(67%), A(27%) | 5 | N | N | N | N | N | N | N | N | N | N | N | N(98%) | 2 | |||||||||||||||||||||||
| 3.46 (104) | √ | s | V | V | I | I(63%), L(20%), V(15%) | 5 | V | V | I/V | L | L/T | L | C | I | V | V | V | V(45%), L(21%), I(17%) | 9 | |||||||||||||||||||||||
| 3.50 (108) | √ | bs | Y | Y | Y | F(59%), Y(38%) | 3 | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y(91%), F(5%) | 3 | |||||||||||||||||||||||
| 6.53 (253) | √ | √ | bs | F | F | F | F(96%) | 3 | F | F/Y | F | F | F | F | F | F/Y | Y | F/Y | Y | F(71%), Y(25%) | 4 | ||||||||||||||||||||||
| 6.54 (254) | √ | √ | b | √ | T | S | S | S(57%), T(26%) | 6 | S | S | S | S | S | S | S | S | S | S | S | S(88%), A(10%) | 4 | |||||||||||||||||||||
| 6.56 (256) | √ | bs | S | T | S | S(81%), T(10%), G(5%) | 5 | G | G | G | A | G/A | A | A | S/G | G | S | S | G(58%), S(24%), A(19%) | 3 | |||||||||||||||||||||||
| 6.59 (259) | √ | s | F | V | G | F(27%), V(20%), M(18%), I(10%), G(9%), A(7%) | 11 | F | F | F | Q | L | L | L | W | F | F | W | F(48%), L(19%), W(15%) | 11 | |||||||||||||||||||||||
| 6.61 (261) | √ | s | A | V | G | I(31%), V(26%), A(10%), S(9%), T(7%), G(7%), C(7%) | 9 | V | V | V | C | C/S/A | A | A | G | G | G | G | G(38%), V(20%), A(11%), S(10%), C(8%), T(5%) | 10 | |||||||||||||||||||||||
| 7.38 (286) | √ | √ | N | N | D | N(50%), D(40%), T(8%) | 6 | N | N | N | N | N | N | N | N | N | N | N | N(88%), D(9%) | 3 | |||||||||||||||||||||||
| 8.56 (351) | √ | √ | A | A | A | A(98%) | 5 | L | L | L | L | L | L | L | L | L | L | L | L(92%) | 4 | |||||||||||||||||||||||
| 8.59 (354) | √ | √ | T | S | S | T(77%), S(21%) | 5 | D | D | D | D | D | D | D | D/G | D | S | D | D(56%), G(25%), S(11%) | 7 | |||||||||||||||||||||||
| 8.60 (355) | √ | s | √ | S | S | S | S(90%), T(8%) | 3 | S | S | S/F | S | S | S | S | T | S | S | S | S(83%), T(15%) | 3 | ||||||||||||||||||||||
| 8.63 (358) | √ | s | A | S | N | S(80%), A(6%), T(5%), N(5%) | 7 | G | G | A/G | V | V/C | V | V | A/C | A | G | A | A(23%), C(13%), G(39%), V(22%) | 6 | |||||||||||||||||||||||
| 8.64 (359) | √ |
| s |
|
|
I
|
Q
|
M
| M(38%), L(36%), I(21%) | 7 | G | G | G | C | T/C | E | G | L/T | F | N | S | G(23%), T(19%), I(14%), L(8%), M(7%), C(7%), N(6%) | 12 | ||||||||||||||||||||
√, indicates whether these residues contact leucine or sodium via backbone atoms, side-chain atoms, or both.
The moiety of the substrate that is involved in the interactions is indicated with “b” (backbone), “s” (side-chain), or “bs” (both).