3NM0: Structure of rat neuronal nitric oxide synthase heme domain in complex with 6-(((3R,4R)-4-(2-(2,2-Difluoro-2-phenylethylamino)ethoxy) pyrrolidin-3-yl)methyl)-4-methyl-3,4,5,6-tetrahydropyridin-2-amine

In our efforts to discover neuronal isoform selective nitric oxide synthase (NOS) inhibitors, we have developed a series of compounds containing a pyrrolidine ring with two stereogenic centers. The enantiomerically pure compounds, (S,S) versus (R,R), exhibited two different binding orientations, with (R,R) inhibitors showing much better potency and selectivity. To improve the bioavailability of these inhibitors, we have introduced a CF(2) moiety geminal to an amino group in the long tail of one of these inhibitors, which reduced its basicity, resulting in compounds with monocationic character under physiological pH conditions. Biological evaluations have led to a nNOS inhibitor with a K(i) of 36 nM and high selectivity for nNOS over eNOS (3800-fold) and iNOS (1400-fold). MM-PBSA calculations indicated that the low pK(a) NH is, at least, partially protonated when bound to the active site. A comparison of rat oral bioavailability of the difluorinated compound to the parent molecule shows 22% for the difluorinated compound versus essentially no oral bioavailability for the parent compound. This indicates that the goal of this research to make compounds with only one protonated nitrogen atom at physiological pH to allow for membrane permeability, but which can become protonated when bound to NOS, has been accomplished.
PDB ID: 3NM0Download
MMDB ID: 88058
PDB Deposition Date: 2010/6/21
Updated in MMDB: 2017/11
Experimental Method:
x-ray diffraction
Resolution: 1.81  Å
Source Organism:
Similar Structures:
Biological Unit for 3NM0: dimeric; determined by author and by software (PISA)
Molecular Components in 3NM0
Label Count Molecule
Proteins (2 molecules)
Nitric Oxide Synthase, Brain(Gene symbol: Nos1)
Molecule annotation
Chemicals (9 molecules)
* Click molecule labels to explore molecular sequence information.

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