10.12.2012 Views

netLibrary - eBook Summary Structure-based Drug Design by ...

netLibrary - eBook Summary Structure-based Drug Design by ...

netLibrary - eBook Summary Structure-based Drug Design by ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Document<br />

Page 300<br />

polypeptides BDS I and II [40,41], which were claimed to have antihypertensive and antiviral activity,<br />

and the α-scorpion toxins [24,27,42]. As discussed below, we may expect to obtain some useful<br />

information from comparisons of the molecular surfaces of these different classes of polypeptides, but<br />

the utility of this approach depends on the extent to which their binding sites are identical and not just<br />

partially overlapping, as well as the issue of channel sub-type specificity of the different toxins.<br />

The synthetic agent DPI 201-106 has been evaluated extensively as a potential replacement for digoxin<br />

[43]. It is a potent positive inotrope that also acts <strong>by</strong> delaying inactivation of the sodium channel, but its<br />

binding site appears to be distinct from that of ATX II [44]. Moreover, it exerts antihypertensive and<br />

local anesthetic effects and may also antagonise the calcium channel [43]. At present we are not aware<br />

of any low molecular mass compound that binds to the same site as the anthopleurins. This offers the<br />

prospect that a mimetic <strong>based</strong> on the anthopleurins might have a pharmacological profile distinct from<br />

other positive inotropes.<br />

The structure of the receptor for the anthopleurins, the α-subunit of the voltage-gated sodium channel, is<br />

known only in schematic form [35–37]. As illustrated in Figure 3, it contains four homologous domains,<br />

each consisting of six transmembrane regions (assumed to be helices) designated S1 to S6. The S4<br />

segments are thought to act as the voltage sensors of the channel. All four<br />

Figure 3<br />

Schematic of the α-subunit of the voltage-gated sodium channel, <strong>based</strong> on its amino<br />

acid sequence [35–37]. The transmembrane segments S1–S6 in each domain are<br />

thought to form helices—with the positively charged S4 segment acting as a<br />

voltage sensor—and the S5–S6 loop of each domain is thought to contribute to the<br />

transmem-brane pore. Site 3 includes regions of the S5–S6 loops of domains I<br />

and IV, and the inactivation gate (h) is located on the intracellular segment linking<br />

domains III and IV.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_300.html (1 of 2) [4/5/2004 5:20:56 PM]

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!