TABLE 1.

Mechanical properties of MreB and F-actin^a

Cytoskeleton protein	Mean ± SD			Exponent G′(c) ∼ c	pH	Source or reference
	Elasticity (dyn/cm2)	Phase angle (°)	Resilience (%)
F-actin	10 ± 3	30 ± 5	10 ± 2	1.2	8.0	45
GTP-MreB	22 ± 3	17 ± 4	3 ± 1	0.29	7.0	This work
ATP-MreB	24 ± 4	15 ± 4	3 ± 1	0.44	7.0	This work

^aElasticity, G′, and phase angle, δ, were measured by using a cone-and-plate strain-controlled rheometer, which applied oscillatory shear deformations of small amplitude (1%) and a frequency of 1 rad/s. Rheological parameters G′ and δ were measured at steady state, i.e., after these parameters had reached a steady state after onset of assembly. The phase angle measures the delay in the response of the stress induced in the filament networks by the rheometer. An elastic solid will show no delay (phase angle of 0°); a viscous liquid without elasticity like glycerol will show a maximum delay (phase angle of 90°). The mechanical resilience of cytoskeleton proteins is defined as the shear amplitude at which the elastic modulus started to decrease. The protein concentration for measurements of G′, δ, and mechanical resilience was 24 μM. For the range of concentrations for the concentration-dependent elasticity, G′(c), see the text and reference.