||"Pol III core is a 1:1:1 heterotrimer of the a polymerase, e 3'-5' proofreading exonuclease, and ? subunits (39, 40) (see Table 1). The a subunit (encoded by dnaE) contains the DNA polymerase activity, incorporating 8 nucleotides/second (ntd/s), similar to Pol III core (20 ntd/s) (41). The e (dnaQ) subunit is the proofreading 3'-5' exonuclease. It is interesting to note that without e the processivity of holoenzyme is markedly reduced from >50 kb to about 1.5 kb (42), thereby ensuring that the proofreading e subunit is present during genome duplication. In contrast, the small ? subunit (holE) has no known function besides a slight stimulation of e (43) and the holE gene can be deleted with little consequence (44)."