Chemical characterization and purification of the beta subunit of the DNA polymerase III holoenzyme from an overproducing strain. Journal Article uri icon



  • We have purified the beta subunit of the DNA polymerase III holoenzyme to homogeneity from an overproducing strain (Blanar, M., Sandler, S., Armengod, M., Ream, L., and Clark, A. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 4622-4626). From this procedure we can obtain 100 mg quantities of protein. The beta isolated from the overproducer is indistinguishable from that isolated from wild-type cells in terms of its activity and molecular weight. Partial amino acid sequence analysis has confirmed the DNA sequence of the dnaN gene (Ohmori, H., Kimura, M., Nagata, T., and Sakakibara, Y. (1984) Gene (Amst.) 28, 159-170) and established the sites for initiation and termination of translation. No processing that removes amino acid residues from beta occurs since the active protein begins with the initiating methionine and terminates at the position predicted from the DNA sequence. Our knowledge of the precise amino acid composition has been used to determine the extinction coefficient of beta to be 17,900 and 18,700 cm-1 M-1 at 280 and 277 nm, respectively. The extinction coefficient at 280 nm is reduced to 14,700 cm-1 M-1 under denaturing conditions in guanidine HCl. Conditions have been optimized so that 1 N-ethylmaleimide residue can be incorporated per beta monomer with full preservation of activity.

publication date

  • September 5, 1986

has subject area

Date in CU Experts

  • October 1, 2013 12:09 PM

Full Author List

  • Johanson KO; Haynes TE; McHenry CS

author count

  • 3

Other Profiles

International Standard Serial Number (ISSN)

  • 0021-9258

Additional Document Info

start page

  • 11460

end page

  • 11465


  • 261


  • 25