TY - JOUR
T1 - The oligomeric T4 primase is the functional form during replication
AU - Yang, Jingsong
AU - Xi, Jun
AU - Zhuang, Zhihao
AU - Benkovic, Stephen J.
PY - 2005/7/8
Y1 - 2005/7/8
N2 - Replisome DNA primases are responsible for the synthesis of short RNA primers required for the initiation of repetitive Okazaki fragment synthesis on the lagging strand during DNA replication. In bacteriophage T4, the primase (gp61) interacts with the helicase (gp41) to form the primosome complex, an interaction that greatly stimulates the priming activity of gp61. Because gp41 is hexameric, a question arises as to whether gp61 also forms a hexameric structure during replication. Several results from this study support such a structure. Titration of the primase/single-stranded DNA binding followed by fluorescence anisotropy implicated a 6:1 stoichiometry. The observed rate constant, kcat, for priming was found to increase with the primase concentration, implicating an oligomeric form of the primase as the major functional species. The generation of hetero-oligomeric populations of the hexameric primase by controlled mixing of wild type and an inactive mutant primase confirmed the oligomeric nature of the most active primase form. Mutant primases defective in either the N- or C-terminal domains and catalytically inactive could be mixed to create oligomeric primases with restored catalytic activity suggesting an active site shared between subunits. Collectively, these results provide strong evidence for the functional oligomerization of gp61. The potential roles of gp61 oligomerization during lagging strand synthesis are discussed.
AB - Replisome DNA primases are responsible for the synthesis of short RNA primers required for the initiation of repetitive Okazaki fragment synthesis on the lagging strand during DNA replication. In bacteriophage T4, the primase (gp61) interacts with the helicase (gp41) to form the primosome complex, an interaction that greatly stimulates the priming activity of gp61. Because gp41 is hexameric, a question arises as to whether gp61 also forms a hexameric structure during replication. Several results from this study support such a structure. Titration of the primase/single-stranded DNA binding followed by fluorescence anisotropy implicated a 6:1 stoichiometry. The observed rate constant, kcat, for priming was found to increase with the primase concentration, implicating an oligomeric form of the primase as the major functional species. The generation of hetero-oligomeric populations of the hexameric primase by controlled mixing of wild type and an inactive mutant primase confirmed the oligomeric nature of the most active primase form. Mutant primases defective in either the N- or C-terminal domains and catalytically inactive could be mixed to create oligomeric primases with restored catalytic activity suggesting an active site shared between subunits. Collectively, these results provide strong evidence for the functional oligomerization of gp61. The potential roles of gp61 oligomerization during lagging strand synthesis are discussed.
UR - http://www.scopus.com/inward/record.url?scp=21844446871&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=21844446871&partnerID=8YFLogxK
U2 - 10.1074/jbc.M501847200
DO - 10.1074/jbc.M501847200
M3 - Article
C2 - 15897200
AN - SCOPUS:21844446871
SN - 0021-9258
VL - 280
SP - 25416
EP - 25423
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 27
ER -