DISTRIBUTION OF THE FLAVOHAEMOGLOBIN, HMP, BETWEEN PERIPLASM AND CYTOPLASM IN ESCHERICHIA-COLI

The subcellular distribution of the soluble flavohaemoglobin (HMP) of Escherichia coli has been determined. Cells over-expressing HMP from t he cloned hmp gene on a multicopy plasmid were fractionated by osmotic shock and lysozyme treatment. Spectral analysis of subcellular fracti ons showed the GO-binding haemoprotein to be cytoplasmic. However, Wes tern blotting using antibody raised to purified HMP revealed approxima tely 30% of the protein to be periplasmic in the over-expressing strai n. Western analysis also revealed substantial levels of periplasmic HM P in a strain expressing only chromosomally encoded protein but none i n an hmp mutant. The results are discussed in relation to protein func tion and the similar distribution reported for Vitreoscilla globin.