Purification and characterization of DNA polymerases from Bacillus species

Abstract

DNA polymerases from Bacillus stearothermophilus, Bacillus caldotenax, and Bacillus caldovelox were purified by chromatography on DEAE-cellulose, phosphocellulose, and heparin-Sepharose and obtained in high yield. The enzyme preparations are free of exo- and endonuclease activities. Additional purification steps, e.g., hydrophobic interaction chromatography and chromatography on a Mono Q column or sucrose density gradient centrifugation, are needed to obtain the enzymes in the form of homogeneous 95-kDa proteins. Each of the three organisms possesses a major DNA polymerase activity comparable to DNA polymerase I. The enzymes require Mg2+ (10 to 30 mM) for optimal activity, although 0.4 mM Mn2+ could substitute for magnesium. The optimal reaction temperatures were lowest in B. stearothermophilus (60 to 65 degrees C) and about equal in B. caldovelox and B. caldotenax (65 to 70 degrees C). The thermal stabilities of the enzymes increased in the same order. The DNA polymerase from Thermus thermophilus was isolated for comparison by using a similar procedure. The enzyme was obtained as a homogeneous 85-kDa protein that was also free of exo- and endonucleolytic activities.