Modulation of microtubule assembly by the HIV-1 Tat protein is strongly dependent on zinc binding to Tat

Table 1 Fluorescence intensity decay parameters of apo-Tat and holo-Tat^a

	τ₁ (ns)	α₁ (%)	τ₂ (ns)	α₂ (%)	τ₃ (ns)	α₃ (%)	τ₄ (ns)	α₄ (%)	<τ> (ns)
Apo-Tat	0.21 ± 0.03	25 ± 2	1.35 ± 0.01	35 ± 3	2.60 ± 0.20	19 ± 1	4.5 ± 0.2	21 ± 5	1.96 ± 0.08
Holo-Tat	0.22 ± 0.05	18 ± 4	1.30 ± 0.20	37 ± 3	2.79 ± 0.09	25 ± 3	5.1 ± 0.2	20 ± 3	2.24 ± 0.07

^aExperiments were performed with 1.5 μM Tat proteins in 50 mM Hepes buffer, pH7.5, at 20°C. The lifetimes, τ_i, and relative amplitudes, α_i, are expressed as means for at least three independent experiments. The mean lifetimes were calculated with: ⟨τ⟩ = ∑α_iτ_i. The excitation and emission wavelengths for Trp were set at 295 nm and 350 nm, respectively.