FIG 3.

Helicase-dependent amplification (HDA). HDA uses the UvrD (helicase) (blue triangles) and MutL (accessory protein required for efficient UvrD loading to DNA) enzymes from E. coli to catalyze temperature-independent creation of a single-stranded DNA template for nucleic acid amplification. The UvrD/MutL complex unwinds double-stranded DNA to form an open complex. Single-strand binding proteins (SSB) (red circles) bind to the denatured strands to prevent association of the complementary strands. Specific primers are designed to anneal to the target sequence, and DNA polymerase (gray oval) extends the primers to the generate target amplicon. This amplicon serves as the template for subsequent rounds of amplification. (Adapted from reference 53 with permission [copyright Wiley-VCH Verlag GmbH & Co. KGaA].)