ISOLATION AND CHARACTERIZATION OF A FAMILY OF PORIN PROTEINS FROM HELICOBACTER-PYLORI

Two-dimensional gel electrophoresis was used to identify heat-modifiab le outer membrane proteins, which were candidates for porins, from Hel icobacter pylori membrane preparations, Four such proteins with appare nt molecular masses of 48, 49, 50, and 67 kDa were isolated. The four proteins copurified together after selective detergent solubilizations followed by anion-exchange chromatography, and each protein was ultim ately purified to homogeneity by gel purification, These proteins were then tested for pore-forming ability with a planar lipid bilayer mode l membrane system. All four proteins appeared to be present as monomer s, and they formed pores with low single-channel conductances in 1.0 M KCl of 0.36, 0.36, 0.30, and 0.25 nS, respectively, for the 48-, 49-, 50, and 67-kDa proteins which we propose to designate HopA, HopB, Hop C, and HopD, N-terminal amino acid sequence analyses showed a high deg ree of homology among all four proteins, and it appears that these pro teins constitute a family of related porins in H. pylori.