PLANT PHYSIOLOGY , Vol 102, Issue 2 615-621, Copyright © 1993 by American Society of Plant Biologists
Purification and Characterization of Porin from Corn (Zea mays L.) Mitochondria
J. A. Aljamal, G. Genchi, V. De Pinto, L. Stefanizzi, A. De Santis, R. Benz and F. Palmieri
Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari and Consiglio Nazionale delle Ricerche Unit for the Study of Mitochondria, Bari, Italy (J.A.A., G.G., V.D.P., L.S., F.P)
Mitochondrial porin from corn (Zea mays L. B 73) shoots was solubilized
with lauryl(dimethyl)-amine oxide and purified by chromatography on a
hydroxyapatite:celite column. On sodium dodecyl sulfate-polyacrylamide gel
electrophoresis, the purified protein had an apparent molecular mass of 35
kD. When reconstituted in planar lipid bilayer membranes the porin formed
ion-permeable channels with single-channel conductance of 2.0 and 4.0
nanosiemens in 1 M KCl. At low transmembrane voltages corn porin had the
properties of a general diffusion pore with an estimated effective diameter
of 1.6 nm and a small selectivity for anions over cations. The primary
structure of corn porin seems to be quite different from that of other
mitochondrial porins, because it did not cross-react with monoclonal
antibodies against human porin and with polyclonal antibodies against yeast
porin. Furthermore, the peptide maps of corn and bovine heart porins were
very different. A sequence of 21 amino acids obtained by Edman degradation
of peptides generated by porin proteolysis with Staphylococcus aureus V8
protease did not show any significant homology with known sequences of
mitochondrial porins. Results of our investigation suggest that corn porin
possesses functional properties similar to those of other mitochondrial
porins, despite major structural differences.
