J. Biol. Chem., Vol. 263, Issue 18, 8838-8843, 06, 1988
Radiation inactivation analysis of chloroplast CF0-CF1 ATPase
MY Wang, LF Chien and RL Pan
Institute of Radiation Biology, College of Nuclear Sciences, Taiwan, Republic of China.
Radiation inactivation technique was employed to measure the functional
size of adenosine triphosphatase of spinach chloroplasts. The functional
size for acid-base-induced ATP synthesis was 450 +/- 24 kilodaltons; for
phenazine methosulfate-mediated ATP synthesis, 613 +/- 33 kilodaltons; and
for methanol-activated ATP hydrolysis, 280 +/- 14 kilodaltons. The
difference (170 +/- 57 kilodaltons) between 450 +/- 24 and 280 +/- 14
kilodaltons is explained to be the molecular mass of proton channel
(coupling factor 0) across the thylakoid membrane. Our data suggest that
the stoichiometry of subunits I, II, and III of coupling factor 0 is
1:2:15. Ca2+- and Mg2+-ATPase activated by methanol, heat, and trypsin
digestion have a similar functional size. However, anions such as SO3(2-)
and CO3(2-) increased the molecular mass for both ATPase's (except
trypsin-activated Mg2+-ATPase) by 12- 30%. Soluble coupling factor 1 has a
larger target size than that of membrane-bound. This is interpreted as the
cold effect during irradiation.