FIG. 2.

Alignment of the deduced amino acid sequences of putative 5′-3′ exonuclease domains encoded by pCS1 to pCS8 and by fCS1. The amino acid sequence of the 5′-3′ exonuclease domain of E. coli DNA polymerase I (19) was used as a reference. The six conserved regions of 5′-3′ exonuclease domains described by Gutman and Minton (9) are marked with the letters A to F and are shaded. Positions of conserved aspartate and glutamate resides that are putatively involved in binding of metals (9) are marked by asterisks and are shown in bold letters. The aspartate residue (D116 [E. coli]) which was replaced by asparagine in the cold-sensitive E. coli mutants (16) is indicated by white letters.