TY - JOUR

T1 - Pre-steady-state kinetic and mutational insights into mechanisms of endo- and exonuclease DNA processing by mutant forms of human AP endonuclease

AU - Bakman, Artemiy S.

AU - Ishchenko, Alexander A.

AU - Saparbaev, Murat

AU - Fedorova, Olga S.

AU - Kuznetsov, Nikita A.

N1 - Funding Information: This work was supported partially by a Russian-Government–funded project (No. 121031300041-4 ), by Electricité de France ( RB 2020-02 and RB 2021-05 , to M.S), by French National Research Agency ( ANR-18-CE44-0008 ) and Fondation ARC ( PJA-2021060003796 ) to A.A.I. The part of this work involving Trp detection combined with stopped-flow kinetics was specifically funded by Russian Science Foundation grant No. 21-64-00017 . Publisher Copyright: © 2022

PY - 2022/12

Y1 - 2022/12

N2 - Human apurinic/apyrimidinic endonuclease APE1 catalyzes endonucleolytic hydrolysis of phosphodiester bonds on the 5′ side of structurally unrelated damaged nucleotides in DNA or native nucleotides in RNA. APE1 additionally possesses 3′-5′-exonuclease, 3′-phosphodiesterase, and 3′-phosphatase activities. According to structural data, endo- and exonucleolytic cleavage of DNA is executed in different complexes when the excised residue is everted from the duplex or placed within the intrahelical DNA cavity without nucleotide flipping. In this study, we investigated the functions of residues Arg177, Arg181, Tyr171 and His309 in the APE1 endo- and exonucleolytic reactions. The interaction between residues Arg177 and Met270, which was hypothesized recently to be a switch for endo- and exonucleolytic catalytic mode regulation, was verified by pre–steady-state kinetic analysis of the R177A APE1 mutant. The function of another DNA-binding–site residue, Arg181, was analyzed too; it changed its conformation when enzyme–substrate and enzyme–product complexes were compared. Mutation R181A significantly facilitated the product dissociation stage and only weakly affected DNA-binding affinity. Moreover, R181A reduced the catalytic rate constant severalfold due to a loss of contact with a phosphate group. Finally, the protonation/deprotonation state of residues Tyr171 and His309 in the catalytic reaction was verified by their substitution. Mutations Y171F and H309A inhibited the chemical step of the AP endonucleolytic reaction by several orders of magnitude with retention of capacity for (2R,3S)-2-(hydroxymethyl)-3-hydroxytetrahydrofuran-containing-DNA binding and without changes in the pH dependence profile of AP endonuclease activity, indicating that deprotonation of these residues is likely not important for the catalytic reaction.

AB - Human apurinic/apyrimidinic endonuclease APE1 catalyzes endonucleolytic hydrolysis of phosphodiester bonds on the 5′ side of structurally unrelated damaged nucleotides in DNA or native nucleotides in RNA. APE1 additionally possesses 3′-5′-exonuclease, 3′-phosphodiesterase, and 3′-phosphatase activities. According to structural data, endo- and exonucleolytic cleavage of DNA is executed in different complexes when the excised residue is everted from the duplex or placed within the intrahelical DNA cavity without nucleotide flipping. In this study, we investigated the functions of residues Arg177, Arg181, Tyr171 and His309 in the APE1 endo- and exonucleolytic reactions. The interaction between residues Arg177 and Met270, which was hypothesized recently to be a switch for endo- and exonucleolytic catalytic mode regulation, was verified by pre–steady-state kinetic analysis of the R177A APE1 mutant. The function of another DNA-binding–site residue, Arg181, was analyzed too; it changed its conformation when enzyme–substrate and enzyme–product complexes were compared. Mutation R181A significantly facilitated the product dissociation stage and only weakly affected DNA-binding affinity. Moreover, R181A reduced the catalytic rate constant severalfold due to a loss of contact with a phosphate group. Finally, the protonation/deprotonation state of residues Tyr171 and His309 in the catalytic reaction was verified by their substitution. Mutations Y171F and H309A inhibited the chemical step of the AP endonucleolytic reaction by several orders of magnitude with retention of capacity for (2R,3S)-2-(hydroxymethyl)-3-hydroxytetrahydrofuran-containing-DNA binding and without changes in the pH dependence profile of AP endonuclease activity, indicating that deprotonation of these residues is likely not important for the catalytic reaction.

KW - Active site

KW - Apurinic/apyrimidinic endonuclease

KW - Conformational change

KW - DNA repair

KW - DNA-protein interaction

KW - Fluorescence

KW - Pre-steady-state kinetics

KW - Substrate recognition

UR - http://www.scopus.com/inward/record.url?scp=85137027776&partnerID=8YFLogxK

U2 - 10.1016/j.bbagen.2022.130198

DO - 10.1016/j.bbagen.2022.130198

M3 - Article

C2 - 35809816

AN - SCOPUS:85137027776

VL - 1866

JO - Biochimica et Biophysica Acta - General Subjects

JF - Biochimica et Biophysica Acta - General Subjects

SN - 0304-4165

IS - 12

M1 - 130198

ER -