Inside-out but not right side-out plasma membrane vesicles from
soybean enlarge when treated with ATP + 2,4-D as determined
by electron microscopy and light scattering: Evidence for involvement of a
plasma membrane AAA-ATPase
Affiliations: 1945 Ridgetop Drive, Charlottesville, VA, USA | Department of Medicinal Chemistry and Molecular
Pharmacology, HANS Life Sciences Research Building, Purdue University, 201
South University Street, West Lafayette, IN 47907-2064, USA
Note: [] Address for correspondence: D.J. Morré, Department of
Medicinal Chemistry and Molecular Pharmacology, HANS Life Sciences Research
Building, Purdue University, 201 South University Street, West Lafayette, IN
47907-2064, USA. Fax: +1 765 494 4007; E-mail: morre@pharmacy.purdue.edu
Abstract: The concept that the location of an AAA-ATPase associated with the
plant plasma membrane may be indicative of a functional relationship to growth
or cell enlargement by analogy with roles in physical membrane displacements as
proposed for AAA-ATPases associated with internal membranes was tested. A plant
growth hormone-responsive and nucleoside triphosphate-dependent enlargement of
inside-out vesicles of plasma membranes from soybeans was utilized in a
completely cell-free system. The rate of enlargement was accelerated by the
synthetic plant growth factor 2,4-dichlorophenoxyacetic acid (2,4-D) in a log
dose-dependent manner and was increased approximately 2-fold with the addition
of 1 μM 2,4-D plus 100 μM ATP
compared to 100 μM ATP alone, 1 μM
2,4-D alone or no additions. The cell-free enlargement was inhibited by
AAA-ATPase-specific antisera and by CoCl_{2}, an inhibitor
specific for AAA-ATPases. The responsible ATP site appears to be on the inside
of the cell, since right side-out vesicles did not enlarge in response to
either ATP, 2,4-D or the two in combination.
