Lysine-cysteine NOS bonds: Difference between revisions

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==Methods==
==Methods==
This is a summary of the observations supporting the NOS bond<ref name="wensien2021" />. [[6zx4]] (oxidized form, NOS present) has a [[resolution]] of 0.96 Å, with a better than average [[Rfree|R<sub>free</sub>]] of 0.136. ''Neisseria gonorrhoeae'' transaldolase has 3 cysteines (no disulfide bonds). It does not form disulfide-linked oligomers. Each Cys was individually mutated to Ser. Only the mutation Cys38Ser abolished redox control, producing a constitutively active enzyme.
This is a summary of the observations supporting the NOS bond<ref name="wensien2021" />. [[6zx4]] (oxidized form, NOS present, enzyme inactive) has a [[resolution]] of 0.96 Å, with a better than average [[Rfree|R<sub>free</sub>]] of 0.136. ''Neisseria gonorrhoeae'' transaldolase has 3 cysteines (no disulfide bonds). It does not form disulfide-linked oligomers. Each Cys was individually mutated to Ser. Only the mutation Cys38Ser abolished redox control, producing a constitutively active enzyme.


Electron density for an unidentified atom appeared between the sidechain nitrogen of Lys8 and the sulfur of Cys38 for several crystals under nonreducing conditions, as well as in data from a low-dose non-synchrotron source, arguing against a radiation damage artifact. Competitive refinements indicated that the unidentified atom was oxygen, rather than carbon.
Electron density for an unidentified atom appeared between the sidechain nitrogen of Lys8 and the sulfur of Cys38 for several crystals under nonreducing conditions, as well as in data from a low-dose non-synchrotron source, arguing against a radiation damage artifact. Competitive refinements indicated that the unidentified atom was oxygen, rather than carbon.

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Eric Martz, Michal Harel