Sandbox Reserved 1051: Difference between revisions
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===Ag85C-ebselen=== | ===Ag85C-ebselen=== | ||
[[Image:Ag85 ebselen.jpg |100 xp|left|thumb|'''Figure 3.''' Ag85C-ebselen: Ebselen covalently binds to Cys209 and forces the otherwise kinked alpha-9 helix to take on a relaxed conformation, thus allowing movement of the helix and a reduction in enzymatic activity.]] | [[Image:Ag85 ebselen.jpg |100 xp|left|thumb|'''Figure 3.''' [http://proteopedia.org/wiki/index.php/4qdu Ag85C-ebselen]: Ebselen covalently binds to Cys209 and forces the otherwise kinked alpha-9 helix to take on a relaxed conformation, thus allowing movement of the helix and a reduction in enzymatic activity.]] | ||
<scene name='69/694218/Ag85c-ebselen/1'>Ag85C-ebselen</scene> is characterized by a covalent bond between [http://en.wikipedia.org/wiki/Ebselen ebselen] and Cys209, thus forcing the otherwise kinked helix alpha-9 to take on a relaxed conformation (Figure 3). This allows movement of the helix and causes disruption of the hydrogen bonds within the catalytic triad, ultimately inactivating Ag85C.<ref name="Favrot"/> | |||
These initial findings suggest that ebselen-like mutants characterized by alterations in Cys209 may serve as potential drug targets for ''M. tuberculosis''. Because any modification or mutation of Cys209 in Ag85C leads to either a dramatic decrease or complete loss of enzymatic activity, research suggests there is a low probability of ''M. tuberculosis'' developing resistance to a drug modifying the Cys209. The structures and results of the following mutations and modifications support a strategy for inhibiting the Ag85 complex as a whole with mechanism-based inhibitors that first react with Ser124 to promote the relaxation of alpha-9 helix and expose Cys209 and then react with Cys209 side chain thiol to covalently modify this conserved residue. Such a bifunctional inhibitor would offer specificity while minimizing the probability of selecting for drug resistant mutants.<ref name="Favrot"/> | These initial findings suggest that ebselen-like mutants characterized by alterations in Cys209 may serve as potential drug targets for ''M. tuberculosis''. Because any modification or mutation of Cys209 in Ag85C leads to either a dramatic decrease or complete loss of enzymatic activity, research suggests there is a low probability of ''M. tuberculosis'' developing resistance to a drug modifying the Cys209. The structures and results of the following mutations and modifications support a strategy for inhibiting the Ag85 complex as a whole with mechanism-based inhibitors that first react with Ser124 to promote the relaxation of alpha-9 helix and expose Cys209 and then react with Cys209 side chain thiol to covalently modify this conserved residue. Such a bifunctional inhibitor would offer specificity while minimizing the probability of selecting for drug resistant mutants.<ref name="Favrot"/> | ||
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[[Image:Ag85C Hg.jpg |100 xp|left|thumb|'''Figure 4.''' Ag85C-Hg: A modification of Ag85C generated with the addition of p-chloromercuribenzoic acid compared to the native structure. This modified enzyme lacks a hydrogen bond between Glu228 and His260, which relaxes the kink normally found in the native structure and inhibits the active site.]] | [[Image:Ag85C Hg.jpg |100 xp|left|thumb|'''Figure 4.''' Ag85C-Hg: A modification of Ag85C generated with the addition of p-chloromercuribenzoic acid compared to the native structure. This modified enzyme lacks a hydrogen bond between Glu228 and His260, which relaxes the kink normally found in the native structure and inhibits the active site.]] | ||
The mutant [http://proteopedia.org/wiki/index.php/4qdo Ag85C-Hg] is generated with the addition of [http://en.wikipedia.org/wiki/4-Chloromercuribenzoic_acid p-chloromercuribenzoic acid], the side chain of the complex is disordered due to a lack of hydrogen bonds between Glu228 and His260. Similar to what is observed in Ag85C-ebselen, the alteration in Ag85C-Hg relaxes the kinked helix alpha-9 found in the native structure of the enzyme, thus inhibiting the active site. The ultimate effect is a decrease to only 60% of the normal enzymatic function of Ag85C.<ref name="Favrot"/> | The mutant [http://proteopedia.org/wiki/index.php/4qdo Ag85C-Hg] is generated with the addition of [http://en.wikipedia.org/wiki/4-Chloromercuribenzoic_acid p-chloromercuribenzoic acid], the side chain of the complex is disordered due to a lack of hydrogen bonds between Glu228 and His260. Similar to what is observed in Ag85C-ebselen, the alteration in <scene name='69/694218/Ag85c-hg/1'>Ag85C-Hg</scene> relaxes the kinked helix alpha-9 found in the native structure of the enzyme, thus inhibiting the active site. The ultimate effect is a decrease to only 60% of the normal enzymatic function of Ag85C.<ref name="Favrot"/> | ||
===Ag85C-E228Q=== | ===Ag85C-E228Q=== | ||
