In the biosynthesis of proteins, it is important that the correct tRNA binds to
ID: 483221 • Letter: I
Question
In the biosynthesis of proteins, it is important that the correct tRNA binds to its corresponding amino acid tRNA ligase enzyme. The following data were obtained for the binding of two tRNAs to isoleucine tRNA ligase from E. coli
Substrate
H0 = kJ/mol
S0 = J/mol*K
Isoleucine tRNA
0
+142.0
Valine tRNA
+33.4
+225.7
By what factor is the binding of the correct tRNA favored over the incorrect tRNA at 293 K and 313 K?
Substrate
H0 = kJ/mol
S0 = J/mol*K
Isoleucine tRNA
0
+142.0
Valine tRNA
+33.4
+225.7
Explanation / Answer
substrate
Delta H0(KJ/mol)
Delta So(J/K.mol)
detaG
=deltaH-T*deltaS
(KJ/mol)
Isoleucine tRNA
0
+142.0
42.316KJ/mol(298K)
44.446KJ/mol(313K)
Valine tRNA
+33.0
+225.7
(-34.259KJ at 298K)
(-70.611KJ/mol at 313K)
detaG=deltaH-T*deltaS (KJ/mol)
Delta G for valine tRNA is negative so the binding reaction is spontaneous.
Subsrate+enzyme-->product (forward directed rxn)
substrate
Delta H0(KJ/mol)
Delta So(J/K.mol)
detaG
=deltaH-T*deltaS
(KJ/mol)
Isoleucine tRNA
0
+142.0
42.316KJ/mol(298K)
44.446KJ/mol(313K)
Valine tRNA
+33.0
+225.7
(-34.259KJ at 298K)
(-70.611KJ/mol at 313K)
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