Binding site signatures

Molecular biology studies have identified a loop containing 20-25 amino acid residues between S5 and S6 (or Ml and M2, Fig. 2) forming the pore. The G(Y/F) G motif located in the pore represents the K+-selectivity signature, which is common to all K+ channels. The external entry to the channel pore and its adjacent residues constitute binding sites for toxins and blockers. The internal vestibule of the pore and the adjacent residues in S5 and S6 contribute to binding sites for compounds such as 4-aminopyiidine and quinidine. The S4-S5 linker lies close to the permeation pathway and is required for... 

Figure 1. Schematic drawing of PMCA. Transmembrane regions are numbered 1—10. Domains defined by the SERCA structure are indicated by differential stippling. Within the A-domain alternative splicing occurs predominant variants are indicated for each isoform (Z, X, Y and W indicate 0, 1, 2 and 3 exons included, respectively). Approximate positions of the phosophoryl-aspartate (D ) and the signature lysine (K) of the nucleotide-binding site are shown. In the C-terminal region, the Ca2+-calmodulin binding site is boxed. Shorter a variants (not shown) at the C splice site have lower Ca2+-calmodulin affinity...

The 65-aa DUF 1899 exhibits a prominent cluster of highly conserved (basic) amino acids at the amino terminus representing a coronin signature that has been previously su ested to harbor a putative actin binding site just downstream of a phosphoserine modification site." The three true WD40 domains that follow may vary in some coronin isoforms due to alternative exon splicing and two sequential pseudo domains exhibit much lower detectability by sequence... 

---