%0 Journal Article
%T Correlation between ribonucleoside-diphosphate reductase and three replication proteins in Escherichia coli
%A M Antonia S¨¢nchez-Romero
%A Felipe Molina
%A Alfonso Jim¨¦nez-S¨¢nchez
%J BMC Molecular Biology
%D 2010
%I BioMed Central
%R 10.1186/1471-2199-11-11
%X We tagged NrdB protein with 3¡ÁFLAG epitope and detected its subcellular location by immunofluorescence microscopy. We found that this protein is located in nucleoid-associated clusters, that the number of foci correlates with the number of replication forks at any cell age, and that after the replication process ends the number of cells containing NrdB foci decreases.We show that the number of NrdB foci is very similar to the number of SeqA, DnaB, and DnaX foci, both in the whole culture and in different cell cycle periods. In addition, interfoci distances between NrdB and three replication proteins are similar to the distances between two replication protein foci.NrdB is present in nucleoid-associated clusters during the replication period. These clusters disappear after replication ends. The number of these clusters is closely related to the number of replication forks and the number of three replication protein clusters in any cell cycle period. Therefore we conclude that NrdB protein, and most likely RNR protein, is closely linked to the replication proteins or replisome at the replication fork. These results clearly support the replication hyperstructure model.Initiation of chromosome replication is a key and tightly regulated event in the E. coli cell cycle. Initiation starts by the binding of DnaA protein to the oriC sequence. This facilitates DNA strand opening, and allows the subsequent loading of the primosomal proteins DnaB helicase and DnaG primase, and, finally, the DNA polymerase III holoenzyme, forming the replisomes that will lead to bidirectional chromosome replication [1]. DNA synthesis requires a balanced supply of the four dNTPs in all living cells. NDP reductase (RNR) is an essential enzyme for the synthesis of these precursors in most organisms [2,3]. RNR is a tetramer made of two homodimers - subunit R1 coded by the nrdA gene and subunit R2 coded by the nrdB gene [2]. A body of evidence supports the idea that RNR and the dNTP-synthesizing comp
%U http://www.biomedcentral.com/1471-2199/11/11