In the FMN bound structure, helix α4 is present in the adenine-binding pocket, revealing that movement of this helix and flexibility of the preceding loop allows binding of FAD.
While it directly contacts paromomycin bound to helix 44, its function remains an enigma and its chemical structure remains to be elucidated.
In the loop bound by helix III there are twelve nucleotides, and the purine at position 37 is a G in metazoans.
Additional Lhca Lhca interactions are provided by a short C-terminal segment on the luminal side that binds helix 2 as it exits the membrane, mainly via hydrophobic interactions.
The small-subunit protein Rps14, the yeast homolog of the bacterial S11 protein, directly binds helix 28 of 18S rRNA and is essential for the assembly of 40S ribosomal subunits (Larkin et al, 1987; Moritz et al, 1990).
This analysis was extended (Table 2) by superimposing structures of other α-helix binding EF-hand pairs onto lobe 2 of HsAPC-1 RD independently of the bound α-helix.
(G ) Structure of PcTx1 bound to helix-5 of ASIC1a (PDB 4FZ0).
This light chain bound α-helix consists of a varying number of IQ motifs ([I,L,V]QxxxRGxxx[R,K]) where the light chains, calmodulin or calmodulin-like proteins, bind.
As expected, several of the models predict steric clashes between PcTx1 and neighboring helices within the S1 S4 domain, whereas in others the toxin could be readily accommodated when bound to helix-5.
These three sites bind a helix-loop-helix transcription factor (bHLH), an elongation factor (EF2), and a Myb transcription factor.
