Structural dynamics at the active site of the cancer ‐associated flavoenzyme NQO1 probed by chemical modification with PMSF

We report the crystal structure of NQO1 with phenylmethylsulfonyl fluoride (PMSF) covalently bound to the Tyr128 residue. We show that, unexpectedly, the catalytic activity of the enzyme was not abolished, indicating that the PMSF molecule does not limit the dynamics of this residue. A large conformational heterogeneity of human NAD(P)H:quinone oxidoreductase 1 (NQO1), a flavoprotein associated with various human diseases, has been observed to occur in the catalytic site of the enzyme. Here, we report the X-ray structure of NQO1 with phenylmethylsulfonyl fluoride (PMSF) at 1.6  Å resolution. Activity assays confirmed that, despite being covalently bound to the Tyr128 residue at the catalytic site, PMSF did not abolish NQO1 activity. This may indicate that the PMSF molecule does not reduce the high flexibility of Tyr128, thus allowing NADH and DCPIP substrates to bind t o the enzyme. Our results show that targeting Tyr128, a key residue in NQO1 function, with small covalently bound molecules could possibly not be a good drug discovery strategy to inhibit this enzyme.
Source: FEBS Letters - Category: Biochemistry Authors: Tags: Research Letter Source Type: research