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Figure 1.
Figure 1. Ribbon diagram of the eNOS heme domain, the active
site and the dipeptide inhibitors used in this study. (a)
Chemical structures of the three dipeptide amide or
peptidomimetic NOS inhibitors used in this study: I, L-N^  -nitroarginine-2,4-
L-diaminobutyramide; II
(4S)-N-(4-amino-5-[aminoethyl]aminopentyl)-N'-nitroguanidine;
III, L-N^ -nitroarginine-(4R)-amino-L-proline
amide. (b) Ribbon diagram of eNOS heme domain. All three
isoforms share the similar dimeric fold and have a wide open
solvent-accessible channel connecting the heme active site to
the molecular surface. (c) L-NNA bound in the active site of
eNOS. The extensive hydrogen bonding network (dashed lines)
between L-NNA and enzyme may explain its low-nanomolar potency.
The active site structure and interactions between L-arginine
and the protein are the same in all three mammalian NOS
isoforms. The only exception is Asn368, which is aspartate in
nNOS and iNOS. Even so, the aspartate and asparagine side chains
are oriented in the same way in all three structures.
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