BRUCELLA OMP2A AND OMP2B PORINS - SINGLE-CHANNEL MEASUREMENTS AND TOPOLOGY PREDICTION

Brucella usually carry two highly homologous genes (omp2a and omp2b) f or porin-like proteins. In several B. abortus biovars the omp2a gene h as a large deletion compared to other Brucella omp2's. In this study w e have measured Omp2 pore activity in planar bilayers. Omp2b exhibits well-defined trimeric channel activity whilst Omp2a forms monomeric po res of variable size which are smaller than Omp2b. No sequence homolog y exists between Omp2 and porins of known structure, so hydrophobic mo ment analysis has been used to model their membrane topology. From thi s it appears likely that the deletion removes the crucial L3 internal loop.