dnaC

File:1-s2.0-S0092867413002924-gr5 lrg.jpg

Since dnaC functions as a helicase loader, dnaB helicase is needed. Specifically, for dnaC function a complex with dnaB is formed. dnaB is a hexameric protein{{Cite journal | vauthors = Lanka E, Schuster H | title = The dnaC protein of Escherichia coli. Purification, physical properties and interaction with dnaB protein | journal = Nucleic Acids Research | volume = 11 | issue = 4 | pages = 987–997 | date = 1983-02-25 | pmid = 6298736 | pmc = 325772 | doi = 10.1093/nar/11.4.987 | url = https://academic.oup.com/nar/article/11/4/987/2385140 | issn = 0305-1048 }} with helicase properties that allow it to unwind DNA at the origin site, oriC. When dnaC associates with dnaB and ATP, dnaB and dnaC form dimers with six dnaC polypeptides. This is due to a conformational change of dnaC.{{Cite journal | vauthors = Barcena M, Ruiz T, Donate LE, Brown SE, Dixon NE, Radermacher M, Carazo JM | title = The DnaB·DnaC complex: a structure based on dimers assembled around an occluded channel | journal = The EMBO Journal | volume = 20 | issue = 6 | pages = 1462–1468 | date = 2001-03-15 | pmid = 11250911 | pmc = 145514 | doi = 10.1093/emboj/20.6.1462 | language = en | issn = 0261-4189 }} These dimers a specific structure, containing a small lobe and a large lobe. The small lobe attaches to one monomer of the dnaB, while the large lobe associates with subunits of neighboring dnaB. dnaB transforms from a closed ring structure to an open ring structure with the addition of dnaC and ATP. The binding of the two proteins is because of interactions regarding their amino acids. Amino acids on the N terminus of dnaC associate with the carboxyl terminal domain of dnaB.{{Cite journal | vauthors = Chodavarapu S, Jones AD, Feig M, Kaguni JM | title = DnaC traps DnaB as an open ring and remodels the domain that binds primase | journal = Nucleic Acids Research | volume = 44 | issue = 1 | pages = 210–220 | date = 2016-01-08 | pmid = 26420830 | doi = 10.1093/nar/gkv961 | pmc = 4705694 | url = https://academic.oup.com/nar/article/44/1/210/2499692?login=false | issn = 0305-1048 }} When this happens, there is also a conformational change of the RecA fold on dnaB and the AAA+ domain of dnaC. The RecA fold is responsible for DNA binding and the AAA+ domain of dnaC is needed for ATP binding and hydrolysis. ATP hydrolysis is necessary for the function of dnaC later in replication. Additionally, dnaC impacts hairpins of the N-terminal domain of dnaB and the N-terminal domain of dnaB can be modified by dnaC to impact interactions with dnaG, a primase.{{Cite journal | vauthors = McMillan SD, Keck JL | title = Biochemical characterization of Escherichia coli DnaC variants that alter DnaB helicase loading onto DNA | journal = The Journal of Biological Chemistry | volume = 300 | issue = 5 | pages = 107275 | date = 2024-05-01 | pmid = 38588814 | pmc = 11087952 | doi = 10.1016/j.jbc.2024.107275 | language = English | doi-access = free | issn = 0021-9258 }} The new dnaB-dnaC complex formed can now aid in loading dnaB to the origin of replication.

The dnaB-dnaC complex is able to open and close like a clamp due to its ring-like structure. To start binding, a region in the DNA is unwound slightly by the protein dnaA attached to dnaA boxes. The slight unwinding allows for the dnaB-dnaC complex to associate with the DNA replication fork.{{Cite journal | vauthors = Makowska-Grzyska M, Kaguni JM | title = Primase Directs the Release of DnaC from DnaB | journal = Molecular Cell | volume = 37 | issue = 1 | pages = 90–101 | date = 2010-01-15 | pmid = 20129058 | pmc = 2819048 | doi = 10.1016/j.molcel.2009.12.031 | language = English | issn = 1097-2765 }} These interactions with the replication fork are impacted by the AAA+ domain on the C-terminal domain of dnaC. For single strand binding, ATP hydrolysis of dnaC is needed for the complex to bind to the template ssDNA with a high affinity.{{Cite journal | vauthors = Biswas SB, Biswas-Fiss EE | title = Quantitative Analysis of Binding of Single-Stranded DNA by Escherichia coli DnaB Helicase and the DnaB·DnaC Complex | journal = Biochemistry | volume = 45 | issue = 38 | pages = 11505–11513 | date = 2006-09-01 | pmid = 16981710 | doi = 10.1021/bi060118d | url = https://pubs.acs.org/doi/10.1021/bi060118d | issn = 0006-2960 | url-access = subscription }} ATP is hydrolyzed to ADP and the complex is able to bind and close its ring-like structure around the DNA strand. When the dnaB-dnaC complex initially binds to the DNA, it is inactive. To activate dnaB, dnaC has to be released. When this occurs, dnaB is translocated and can begin unwinding the DNA for replication.

For dnaB to complete helicase activity, dnaC is required to dissociate from the dnaB-dnaC complex. The release of dnaC from dnaB relies on multiple factors. First, a hydrolysis reaction that specifically requires ATP needs to occur.{{Cite journal | vauthors = Wahle E, Lasken RS, Kornberg A | title = The dnaB-dnaC replication protein complex of Escherichia coli. II. Role of the complex in mobilizing dnaB functions | journal = The Journal of Biological Chemistry | volume = 264 | issue = 5 | pages = 2469–2475 | date = 1989-02-15 | pmid = 2536713 | doi = 10.1016/S0021-9258(19)81637-X | doi-access = free | issn = 0021-9258 }} This reaction is the same one used to bind the complex to the ssDNA at the replication fork. In addition, interactions with dnaG on the N-terminal domain of dnaB are necessary to disrupt the dnaB-dnaC complex. This interaction and hydrolysis reaction releases dnaC from the C-terminal domain of dnaB. Once dnaC dissociates from the complex, dnaB is able to perform helicase activities for DNA replication. These allow for the ssDNA to be available to primase and other proteins necessary to create a complementary strand of the template DNA.

Current research is ongoing regarding dnaC and its role in prokaryotic DNA replication. Research groups are using a variety of physical{{Cite journal | vauthors = Pangeni S, Rashid F, Berger J, Ha T | title = BPS2025 - Replicative helicase is a flexible fuel motor | journal = Biophysical Journal | volume = 124 | issue = 3 | pages = 496a | date = 2025-02-13 | doi = 10.1016/j.bpj.2024.11.2611 | url = https://linkinghub.elsevier.com/retrieve/pii/S0006349524033393 | language = English | bibcode = 2025BpJ...124..496P | issn = 0006-3495 | url-access = subscription }} and molecular{{Cite journal | vauthors = Maciag-Dorszynska M, Morcinek-Orlowska J, Baranska S | title = Concise Overview of Methodologies Employed in the Study of Bacterial DNA Replication | journal = International Journal of Molecular Sciences | volume = 26 | issue = 2 | pages = 446 | date = 2025-01-07 | pmid = 39859162 | pmc = 11764726 | doi = 10.3390/ijms26020446 | language = en | doi-access = free | issn = 1422-0067 }} methods to further knowledge. Topics include the role of single stranded binding proteins,{{Cite journal | vauthors = Akama Y, Yoshida R, Ozaki S, Kawakami H, Katayama T | title = SSB promotes DnaB helicase passage through DnaA complexes at the replication origin oriC for bidirectional replication | journal = Journal of Biochemistry | volume = 177 | issue = 4 | pages = 305–316 | date = 2025-04-02 | pmid = 39776183 | pmc = 11952115 | doi = 10.1093/jb/mvaf003 | url = https://academic.oup.com/jb/article/177/4/305/7945642 | issn = 0021-924X }} potentially exploiting the dnaC-dnaB complex for peptide antibiotics,{{Cite journal | vauthors = Zhang Z, Chen J, Yao M, Wang G | title = Structural Insight Into the Function of DnaB Helicase in Bacterial DNA Replication | journal = Proteins | volume = 93 | issue = 2 | pages = 420–429 | date = 2025 | pmid = 39230358 | doi = 10.1002/prot.26746 | url = https://onlinelibrary.wiley.com/doi/10.1002/prot.26746 | language = en | issn = 1097-0134 | url-access = subscription }} interactions with other proteins like dnaE,{{cite bioRxiv | vauthors = O'Neal LG, Drucker MN, Lai NK, Clemente AF, Campbell AP, Way LE, Hong S, Holmes EE, Rancic SJ, Sawyer N, Wang X, Thrall ES | title = The B. subtilis replicative polymerases bind the sliding clamp with different strengths to tune replication processivity and fidelity |biorxiv=10.1101/2025.03.10.642433}} and others. Additionally, other prokaryotic helicase loaders, like DciA in bacteria,{{Cite journal | vauthors = Marsin S, Jeannin S, Baconnais S, Walbott H, Pehau-Arnaudet G, Noiray M, Aumont-Nicaise M, Stender EG, Cargemel C, Le Bars R, Le Cam E, Quevillon-Cheruel S | title = DciA, the Bacterial Replicative Helicase Loader, Promotes LLPS in the Presence of ssDNA | journal = Journal of Molecular Biology | volume = 437 | issue = 2 | pages = 168873 | date = 2025-01-15 | pmid = 39603490 | doi = 10.1016/j.jmb.2024.168873 | url = https://linkinghub.elsevier.com/retrieve/pii/S0022283624005035 | issn = 0022-2836 }} are being investigated due to their similar properties to dnaC.

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{{DNA replication}}

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