Figure 5.
CLASP1 promotes the depolymerization of plus and minus ends in the presence of GTP but is plus-end specific in the presence of GDP. (A) Schematic of the polarity-marked microtubule assay used to distinguish plus and minus ends. (B) Representative kymographs of polarity-marked microtubules incubated with 0, 16, and 250 nM CLASP1. (C) Quantification of microtubule depolymerization rates as a function of CLASP1 concentration in the presence of 1 mM GTP. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from four experimental days. The solid lines represent the Michaelis-Menten fit to the data. (D) Representative kymographs of polarity-marked microtubules incubated with 200 nM CLASP1 in the no nucleotide, 1 mM GTP, and 1 mM GDP conditions. (E) Quantification of microtubule depolymerization rates as a function of GTP concentration in the presence of 200 nM CLASP1. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from three experimental days. The plus-end data are in dark green and the minus-end data are in light green. The solid lines represent the Michaelis-Menten fit to the data. See also Video 2. (F) Quantification of microtubule depolymerization rates as a function of GDP concentration in the presence of 200 nM CLASP1. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from four experimental days. The solid lines represent the Michaelis-Menten fit to the data for the plus end and a linear fit for the minus end. An F test for linear regression was performed to test the statistical significance of the minus-end data (P = 0.08).

CLASP1 promotes the depolymerization of plus and minus ends in the presence of GTP but is plus-end specific in the presence of GDP. (A) Schematic of the polarity-marked microtubule assay used to distinguish plus and minus ends. (B) Representative kymographs of polarity-marked microtubules incubated with 0, 16, and 250 nM CLASP1. (C) Quantification of microtubule depolymerization rates as a function of CLASP1 concentration in the presence of 1 mM GTP. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from four experimental days. The solid lines represent the Michaelis-Menten fit to the data. (D) Representative kymographs of polarity-marked microtubules incubated with 200 nM CLASP1 in the no nucleotide, 1 mM GTP, and 1 mM GDP conditions. (E) Quantification of microtubule depolymerization rates as a function of GTP concentration in the presence of 200 nM CLASP1. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from three experimental days. The plus-end data are in dark green and the minus-end data are in light green. The solid lines represent the Michaelis-Menten fit to the data. See also Video 2. (F) Quantification of microtubule depolymerization rates as a function of GDP concentration in the presence of 200 nM CLASP1. Data are means ± SE; N = 10 microtubules analyzed per condition obtained from four experimental days. The solid lines represent the Michaelis-Menten fit to the data for the plus end and a linear fit for the minus end. An F test for linear regression was performed to test the statistical significance of the minus-end data (P = 0.08).

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