title: Protein n, a primosomal DNA replication protein of Escherichia coli. Purification and characterization.
abstract: Protein n, essential in forming the primosome for the in vitro conversion of phi X174 single-stranded (SS) DNA to the duplex replicative form (RF), has been purified about 5000-fold to near homogeneity from Escherichia coli. Protein n is heat- and acid-resistant and N-ethyl-maleimide-sensitive. It appears to be a dimer of 12,000 (+/- 2000)-dalton polypeptides. About 80 molecules of protein n are present/cell. Protein n binding to phi X SS DNA depends on the presence of single-strand binding protein (SSB). This requirement for SSB reflects a direct interaction of protein n and SSB. About 30 protein n monomers can be bound to an SSB-coated circle. However, in forming the primosome on an SSB-coated phi X circle, an input of only 2-3 protein n monomers is required and 1 monomer bound/circle. Retention of this low level of protein n on SSB-coated phi X SS DNA is dependent upon protein n', a DNA-dependent ATPase (dATPase) that guides primosome assembly. This single protein n monomer is retained in the assembled primosome, which is conserved on the completed parental RF and participates in the next stage of the replicative cycle, production of progeny RF.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification*; D010584:Bacteriophage phi X 174; D002352:Carrier Proteins; D004261:DNA Replication; D004268:DNA-Binding Proteins; D004355:Drug Stability; D004926:Escherichia coli / Q000235:genetics*; D007700:Kinetics; D008970:Molecular Weight; D011487:Protein Conformation
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins