Abstract
Decreasing the NaCl concentration from 3 to 0.5% or lower in the growth medium caused a drastic change in the ratio of the two outer membrane proteins b and b′ with respective apparent molecular weights of about 36, 000 and 35, 000: the amounts of proteins b and b′ decreased and increased, respectively. However supplementation of the growth medium with high concentrations of sucrose did not affect the synthesis of the two proteins. Both proteins were not solubilized with 2% sodium dodecyl sulfate at 50°C for 30min and resistant to trypsin, indicating that they are porin-like proteins. Their peptide fragments created by limited proteolysis with Staphylococcus aureus V8 protease, their amino acid compositions and their antigenecity differed from each other. Only one major porin-like protein, b′, was formed in the cells grown on 0.2% NaCl-nutrient broth, and pentose and hexose diffused through the outer membrane freely but di-, tri-, tetra- and pentasaccharides did not. On the other hand, when the cells were grown in synthetic medium which substantially contain protein b as the only one major porin-like protein, pentose and hexose penetrate the outer membrane freely, di- and tri- saccharides diffused partly but tetra- and pentasaccarides did not.
