Single molecule TPM analysis of the catalytic pentad mutants of Cre and Flp site-specific recombinases: contributions of the pentad residues to the pre-chemical steps of recombination.
Bottom Line: The pentad residues in Cre enhance commitment to recombination by kinetically favoring the formation of pre-synaptic complexes.Kinetic comparisons between Cre and Flp, and between their derivatives lacking the tyrosine nucleophile, are consistent with a stronger commitment to recombination in the Flp system.The integrity of the synapse, whose establishment/stability is fostered by strand cleavage in the case of Flp but not Cre, appears to be compromised by the pentad mutations.
Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang Ming University, Taipei 112, Taiwan firstname.lastname@example.org.Show MeSH
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Mentions: The kinetic constants for Cre and Cre(K201A) were determined in previous work (24). The values for all other proteins were determined from time traces of individual molecules represented in the data shown in Figures 3–6. The rate constants for recombination (column 6) by Cre(H289A) and Cre(W315F) were obtained from the data in panel E of Figures 4 and 6, respectively, by fitting them to a double exponential model (Materials and Methods). An independent estimate of the rate constant for recombination by Cre(W315F) using a DNA substrate containing head-to-head loxP sites gave a value close to that shown here (Supplementary Figure S4). kPSf = rate constant for the formation of pre-synaptic complexes; kRSf = rate constant for the formation of recombination-competent synaptic complexes; kWWf = rate constant for the formation of wayward synaptic complexes; k*WWf = rate constant for the formation of long-lived wayward complexes assembled by Cre(K201A); kWWd = rate constant for the decomposition of wayward complexes; k*WWd = rate constant for the decomposition of long-lived wayward complexes formed by Cre(K201A); kREC = rate constant for recombination (conversion of synaptic complexes into recombinant products).
Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang Ming University, Taipei 112, Taiwan email@example.com.