(4pts) A vegetative storage protein (VSP2) from the model plant Arabidopsis thal
ID: 91891 • Letter: #
Question
(4pts) A vegetative storage protein (VSP2) from the model plant Arabidopsis thaliana (At) was purified as a wild-type (AtVSP2) and a recombinant protein (Nus-AtVSP2). D119E is an aspartic acid to glutamic acid substitution at amino acid position 119. The phosphatase activity was measured under different pH conditions (adapted from Liu et. al. Plant Physiol. 2005;139:1545-1556).
What scientific conclusions can be made about the adding the Nus recombinant tag to AtVSP2? (Do not just describe the graph. A scientific conclusion should include an interpretation of the data.) Propose a reasonable scientific hypothesis for the observed effect of the D119E mutation on the phosphatase activity.
100, -O-Nuss-AtVSP2 80 Nus-AtVSP2 (D119E) --Nus 60 E 40 2 20- 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 pHExplanation / Answer
from the graph-
1) this is an acid phosphatase protein (works under acidic condition (pH 3 to 6 range).
2) wild type has broader pH activity range than recombinant one.
3) activity of wild type protein is maximum at pH - 4 while recombinant protein has pH - 4.5 and activity is around 95% (approx).
4) Nus recombinant tag itself has no activity.
5) Nus tagged recombinant mutated (D119E) protein has no activity. a possible reason for this is, the mutation is in the active site and the increased length interfere with the interactions between the substrate or within the protein itself to gain its activity.
thus Nus protein has no role in the activity. might be this protein helps in stabilizing the protein in cells or helps in the purification process.
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