PURIFICATION, PROPERTIES AND PHYSIOLOGICAL REGULATION OF A PUTATIVE OUTER-MEMBRANE PORIN FOR METHANOL IN METHYLOPHILUS-METHYLOTROPHUS

A major outer-membrane protein was purified and partially characterise d from the methylotrophic bacterium Methylophilus methylotrophus. The protein had a subunit M-r of 38 000 and was similar in terns of its bi ochemical properties to the recently characterised amide-urea porin (F mdC) from the same organism. Expression of the protein, as determined by SDS-PAGE and Western blotting of cells grown in continuous culture under various nutrient limitations, varied in a similar manner to that of methanol dehydrogenase and was maximal under methanol limitation. It was concluded that the protein is probably an outer-membrane porin for methanol.