DNA POLYMERASE-III ACCESSORY PROTEINS .3. HOLC AND HOLD ENCODING CHI AND PSI

Genes encoding the chi and psi accessory proteins of the DNA polymeras e III holoenzyme replicase of Escherichia coli have been identified, s equenced, and used to express and purify both chi and psi in quantity. The holC gene encoding chi is located between the xerB and valS genes at 96.5 min on the chromosome; it encodes a 147-amino acid protein of 16.6 kDa. holD encoding psi lies upstream of rimI at 99.3 min and enc odes a 137-amino acid protein of 15.2 kDa. The genes have been cloned into expression vectors, and both chi and psi have been purified in qu antity. The accompanying report characterizes the function and physica l interactions of chi and psi with other holoenzyme subunits (Xiao, H. , Dong, Z., and O'Donnell, M. (1993) J. Biol. Chem. 268, 11779-11784).