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Figure 5.
Figure 5. Solution oligomerization and kinetic properties of
yeast Hst2 proteins. (a) Equilibrium sedimentation data for
untagged native yHst2 fit with data from nine curves (three
protein concentrations at three centrifugation speeds). A
representative run at a centrifugation speed of 21,425g and
three protein concentrations of 1.75, 2.0 and 2.25 mg ml-1 is
shown. The plots represent a monomer-trimer model for which all
nine curves were fit to a single dissociation constant. Bottom
panels, experimental data (  )
with calculated fits (lines). Top panels, residuals of the fits.
The monomer-trimer K[d] parameters calculated for yHst2 and
His-yHst2 were 1.12  10^-8
M (  2.08
10^-9
M) and 3.44 10^-9
M (4.94 10^-9-2.40
10^-9
M), respectively; the monomer-dimer K[d] parameter calculated
for yHst2-  N7
was 6.46 10^-6
M ( 1.75
10^-6
M). (b) Kinetic analysis of yHst2 and truncation mutants.
Initial velocity pattern is shown in the double reciprocal plot
in which 1/velocity is plotted against 1/[fluorogenic
acetyl-lysine substrate] for the proteins yHst2 (cyan  ),
yHst2- N7
(green  )
and yHst2- C64
(  ).
(c) Inhibition of yHst2 and truncation mutants by acetylated
histone H4 peptide. K[m,app] is determined at various histone H4
peptide concentrations and plotted against the concentration of
H4. Linear fits for the proteins His[6]-tagged yHst2 (cyan ),
untagged yHst2 (  diamond
) and untagged yHst2- 7
(green )
are shown.
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