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. Author manuscript; available in PMC: 2013 Sep 11.
Published in final edited form as: Biochemistry. 2012 Aug 31;51(36):7173–7188. doi: 10.1021/bi3010945

Figure 5.

Figure 5

(A) The formation of TpT, TpTSO2 −, 5'-dA as well as the consumption of SAM in the WT SPL reaction. 5 equivalents of SAM were added to initiate the reaction. A background level of TpTSO2− was observed along with the formation of TpT. The ratio between the SP repair products (TpT +TpTSO2−) and 5'-dA is found to be 1.5 : 1 for the WT SPL reaction, suggesting that SAM is partially catalytic here. (B) The formation of TpT, TpTSO2−2, 5'-dA as well as the consumption of SAM in the SPL C141A reaction with 5 equivalents of SAM supplemented. The ratio between the SP repair products (TpT +TpTSO2−) and 5'-dA was found to be 1.08 : 1 for the SPL C141A reaction, suggesting that SAM plays a non-catalytic role in the C141A reaction and is a co-substrate. Under the 5 equivalents of SAM, the SP TpT repair rate by WT SPL was determined to be 0.41 ± 0.03 min−1, and by SPL C141A mutant was determined to be 0.14 ± 0.02 min−1.