Problem Set 5 Key

Do any of them have a role in the catalysis explain

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Unformatted text preview: st structure that was used to study “this” reaction. What is “this” mechanism? Describe the mechanism this paper suggested with key components by drawing out an e- pushing diagram. (7 points) Inversion mechanism: An acidic residue is required as a general base to activate nucleophilic acceptor species by deprotonation. The deprotonation along with divalent metal ions (Mg2+ and Mn2+) facilitates departure of the 3 nucleotide- diphospho leaving group from nucleotide- diphospho- α- D- sugars. Overall reaction is believed to be SN2 substitution with an oxocarbenium ion transition state. General inverting mechanism with specified general base and metal ions to BsSpsA will get credit. iii. Make a figure of the active site of SpsA indicating the interactions, including the distances, between active site residues (at least 9 resi), divalent metal ions and substrate. What are the three invariant residues within the active site of SpsA? Do any of them have a role in the catalysis? Explain. What is the proposed residue that acts as the catalytic base? Why by the paper was this residue? (5 points) Tyr11, Asp39, and Asp99 are invariant residues within the active site of SpsA. Tyr11 is involved in stacking with the nucleotide base, Asp39 in UDP binding, and Asp99 in coordinating the leaving group, Mn2+ ion, and assisting its departure in the mechanism. The authors suggested Asp191 as the catalytic base because it is in an ideal location and may interact with the glycerol molecule in a similar way to its coordination of the natural...
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This note was uploaded on 01/09/2014 for the course CH 170A taught by Professor Clemens during the Fall '13 term at Caltech.

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