Domain architecture graph for the S-helix. The ordered graph for the contextual information contained in domain fusions, drawn using Pajek  and modified with CorelDraw, is shown. The direction of the edge denotes the order of the fusion of domain in the polypeptide. If a domain is found on either side of another domain in different architectures, the edge points in both the direction. Domains with tandem repeats have loops pointing to themselves. The loop on TM includes bacterial 7TM receptors, 9TM receptors and 12TM Na+/proline symporters (found fused to bacterial histidine kinases in proteobacteria) with multiple successive TM segments separated by short hydrophilic loops. All connections to the S-helix are shown in red, while the other connections are in black. Domain abbreviations are as shown in section 2 Materials and Method or: SH – S-helix, Cyclase-NMP cyclase, HisKin – Histidine Kinase (including the DHp module), DISMED1 (for 7TMR-DISM extracellular domains 1); STYKIN – S/T/Y Kinase; NarQ – Extracellular nitrate sensing domain domain found in NarQ family of proteins; Glo – Globin domain and Hem – Hemerythrin.