Difference between
Biological Activities and Secondary Structures of Expression Product of atpE Gene from
Broad Bean and Maize Chloroplast
WANG Da-Fu, WEI Jia-Mian*
( Shanghai Institute of Plant Physiology, Chinese Academy of
Sciences,Shanghai 200032,China )
Abstract The
chloroplast atpE genes from broad bean and maize were overexpressed in
E.coli, respectively. After proper refolding and purification, two
types of ε-subunit proteins with biological activity were obtained. When
reconstituted with CF1(-ε)from different chloroplast ATPase, the
effects of the reconstructed ε-subunit protein of maize CF1 to the
Ca2+-ATPase activity of ε-deficient CF1 and to the proton
leakage through CF0 were markedly stronger than that of broad bean
CF1. It was also observed that the enhancing effect of maize
ε-subunit protein to the chloroplast photophosphorylation activity was greater
than that of broad bean ε-subunit protein. The results indicate that：(1)the inhibition of ε-subunit
is closely related to the its affinity with other parts of CF1； (2)both functions of
ε-subunit as inhibitor of ATPase and as proton pathway are closely linked. The
circular dichroism was performed to show the differences in their secondary
structure of these ε-subunit proteins based on the deduced primary sequences.
Unconstrained analysis of the CD spectrum for the maize ε-subunit protein gave
22.6% α-helix, 30.6% β-sheet, 9.3% β-turn, and 37.7% unordered structure； and 31.4%α-helix, 22.3%
β-sheet, 13.8% β-turn, and 32.4% unordered structure for the ε-subunit from
broad bean.
Key words ATP synthase；atpE gene；ε-subunit；photophosphorylation；circular dichroism
*Corresponding author：Tel,86-21-64042090-4519；Fax,86-21-64042385；e-mail，[email protected]