{'fraction_non_alphanumeric': 0.018691588785046728, 'fraction_numerical': 0.013743815283122594, 'mean_word_length': 5.431095406360424, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Revealing dynamics of helicase translocation on single-stranded DNA using high-resolution nanopore tweezers

Significance DNA helicases are enzymes that use energy from ATP hydrolysis to move along nucleic acid tracks and unwind double-stranded DNA. Helicases are involved in every aspect of DNA metabolism and are therefore vital to maintaining genomic integrity. Using the single-molecule technique single-molecule picometer-resolution nanopore tweezers (SPRNT), which measures the position of DNA through the biological membrane protein MspA as an enzyme moves along the DNA, we monitored the kinetics of the helicase Hel308 at 1,000 times better temporal resolution than was previously possible. We derived a detailed mechanism for how ATP hydrolysis coordinates the motion of Hel308 along single-stranded DNA that can likely be applied to other structurally similar helicases and showed that the DNA sequence in Hel308 affects its kinetics. Enzymes that operate on DNA or RNA perform the core functions of replication and expression in all of biology. To gain high-resolution access to the detailed mechanistic behavior of these enzymes, we developed single-molecule picometer-resolution nanopore tweezers (SPRNT), a single-molecule technique in which the motion of polynucleotides through an enzyme is measured by a nanopore. SPRNT reveals two mechanical substates of the ATP hydrolysis cycle of the superfamily 2 helicase Hel308 during translocation on single-stranded DNA (ssDNA). By analyzing these substates at millisecond resolution, we derive a detailed kinetic model for Hel308 translocation along ssDNA that sheds light on how superfamily 1 and 2 helicases turn ATP hydrolysis into motion along DNA. Surprisingly, we find that the DNA sequence within Hel308 affects the kinetics of helicase translocation.