Isolation of a Complex between the P Protein of Phage lamba and the dnaB Protein of Escherichia coli

Abstract

P protein of phage .lambda. and dnaB protein of E. coli were isolated from bacteria containing an inducible .lambda. P gene on a plasmid and phage-.lambda.-infected bacteria. P protein from both sources copurifies with part of the dnaB protein during 4 purification steps. A highly purified preparation contains the multimeric dnaB and the P protein in a complex as revealed by glycerol gradient centrifugation. The complex is composed of 2 major polypeptides. Their MW of 52,000 and 26,000 are identical to those previously determined for the dnaB and P polypeptides, respectively. The complex contains a DNA-dependent ribonucleoside triphosphatase activity which can be inactivated by anti-dnaB globulin. Both the dnaB complementing and the ribonucleoside triphosphatase activities are partially masked by the P protein as shown by their stimulation following a treatment with NaCl and N-ethylmaleimide.