Table 1.

ATPase and Motility Properties of Coiled-Coil Mutants

	MT-stimulated ATPase		MT gliding
Construct	K m(MT)	k cat
	μM	ATP/s per head	μm/s
Wild type	0.44 ± 0.09	45 ± 3	0.37 ± 0.11
H1Q	0.41 ± 0.10	35 ± 2	0.44 ± 0.09
H5Q	1.65 ± 0.13	33 ± 1	0.38 ± 0.12
5Lys	1.14 ± 0.33	27 ± 2	0.35 ± 0.05
4Glu	>10	>6	0.47 ± 0.05

K _m(MT) and k _cat indicate the microtubule concentration needed for half-maximal stimulation of the ATPase activity and the maximal ATPase activity at saturating microtubule concentrations, respectively. These values were obtained by fitting ATPase rates measured at eight different microtubule concentrations to a Michaelis-Menten function. Errors are given as the standard error of the fitted parameter. The ATPase activity of the 4Glu mutant did not saturate at up to 25 μM microtubule concentration, and displayed a turnover rate of 6 s⁻¹ at that microtubule concentration. Because of their low microtubule affinity, K _m(MT) and k _cat could not be determined.