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 />

Figure 8<br />

Cartoon representation of the HIV PR dimer. The sites of compensatory<br />

mutations are indicated.<br />

substrate. Also, the reported compensatory mutations are conservative in nature and have no effect on<br />

the overall distribution of atomic charges on the surface of HIV PR.<br />

Page 31<br />

Sequence polymorphism at the Leu63/63' position, located on the surface at the base of HIV PR, has<br />

been observed in clinical isolates of the virus not exposed to any HIV PR inhibitors. Variations of<br />

Ala71/71', where the side chains are buried very close to Leu63/63', are less commonly found in clinical<br />

isolates. After a prolonged challenge <strong>by</strong> HIV PR inhibitors, Leu63/63' changes to proline and Ala71/71'<br />

to valine.<br />

The side chains of Met46/46' are fully exposed to solvent and these residues are located on the βhairpins<br />

that form the active side flaps. It has been speculated that the compensatory change of<br />

Met46/46' to isoleucine or phenylalanine may affect the dynamics of the flap movement, which in turn<br />

could influence the rates of catalytic activity of HIV PR impeded <strong>by</strong> the primary mutations in the active<br />

site [58].<br />

Any changes to Asn88/88' and Leu90/90', buried in the body of HIV PR, most likely affect the structural<br />

stability of the enzyme. The side chains of Asn88/88' form buried hydrogen bonds and replacement of<br />

this residue <strong>by</strong> aspartic acid or serine not only eliminates some of these bonds but also introduces<br />

unfavorable interactions in the core of HIV PR. Similarly, Leu90/90' is buried in a tight hydrophobic<br />

space close to the “fireman's grip” motif, which<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_31.html (1 of 2) [4/5/2004 4:46:51 PM]

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

Saved successfully!

Ooh no, something went wrong!