N-terminal-mediated oligomerization of DnaA drives the occupancy-dependent rejuvenation of the protein on the membrane.
DnaA, the initiator of chromosome replication in most known eubacteria species, is activated once per cell division cycle. Its overall activity cycle is driven by ATP hydrolysis and ADP-ATP exchange. The latter can be promoted by binding to specific sequences on the chromosome and/or to acidic phospholipids in the membrane. We have previously shown that the transition into an active form (rejuvenation) is strongly co-operative with respect to DnaA membrane occupancy. Only at low membrane occupancy is DnaA reactivation efficiently catalysed by the acidic phospholipids. The present study was aimed at unravelling the molecular mechanism underlying the occupancy-dependent DnaA rejuvenation. We found that truncation of the DnaA N-terminal completely abolishes the co-operative transformation between the high and low occupancy states (I and II respectively) without affecting the membrane binding. The environmentally sensitive fluorophore specifically attached to the N-terminal cysteines of DnaA reported on occupancy-correlated changes in its vicinity. Cross-linking of DnaA with a short homobifunctional reagent revealed that state II of the protein on the membrane corresponds to a distinct oligomeric form of DnaA. The kinetic transition of DnaA on the membrane surface is described in the present study by a generalized 2D condensation phase transition model, confirming the existence of two states of DnaA on the membrane and pointing to the possibility that membrane protein density serves as an on-off switch in vivo. We conclude that the DnaA conformation attained at low surface density drives its N-terminal-mediated oligomerization, which is presumably a pre-requisite for facilitated nt exchange.
Department of Life Sciences, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel aaranov@bgu.ac.il.
Alexander
A
Aranovich
Department of Biotechnology Engineering, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel.
Shani
S
Braier-Marcovitz
Department of Chemistry, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel.
Esti
E
Ansbacher
Department of Biotechnology Engineering, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel.
Rony
R
Granek
Department of Chemistry, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel Department of Biophysical Chemistry, NYU-Shanghai, Pudong, Shanghai 200122, PR China.
Abraham H
AH
Parola
Department of Life Sciences, Ben-Gurion University of the Negev, P.O.B. 653, Beer-Sheva 8410501, Israel.
Itzhak
I
Fishov
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D044367:Phase Transition; D011487:Protein Conformation; D055503:Protein Multimerization
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria
bacterial cell cycle; conformation; cross-linking; initiation of deoxyribonucleic acid (DNA) replication; macromolecular crowding; protein-membrane