Arch. Mikrobiol. 81,273--288 (1972) 9 by Springer-Verlag 1972 Isolation, Partial Characterization of the Cytoplasmic Membrane Fraction of Streptomyces albus G and DD-Carboxypeptidase Localization EMILIO MU~OZ, ALBERTO MARQUET, VICENTE LARRAGA, a n d JACQUES COYETTE Instituto de Biologla Celular, C.S.I.C., Madrid, Spain Service de Bacteriologic, Universit6 de Liege, Belgium Received July 15, 1971 Summary. 1. Treatment of Streptomyees albu8 G with lysozyme (mg dry weight mycelium/mg lysozyme ~ 2--3/1) leads to the isolation of membrane fractions whose yields amount to 12--20% of the total celullar protein depending upon the age and state of the bacterial culture. 2. The isolated fractions are composed of 52.7 per cent protein and 41 per cent lipid with minor amounts of hexose (2.3--2.4o/0), hexosamines (1.6--2.1~ RNA (2 ~ ) and DNA (0.45 ~ ). They possess a chemical composition similar to that of other membrane systems. 3. NADH oxidase activities are associated with the membrane fractions from cells of 18--20 h of age. These activities are not detected in the membrane fractions from older cells. 4. All membrane fractions shape small vesicles. Differences in size and shape are, however, found between membrane preparations from cells of distinct ages. 5. DD-carboxypeptidase is not selectively localized in a membrane fraction of a certain age. The subcellular distribution of this activity is similar to that of other lyric endopeptidases of S. albus G. 6. The amounts of nD-carboxypeptidase associated with the various membrane fractions are variable and never very high. The specificity of the nn-carboxy- peptidase activity associated with membrane fractions differs from that of the soluble enzyme. 7. These results are discussed in relationship with the carboxypeptidase-trans- peptidase hypothesis (Leyh-Bouille et al., 1970). For the past 10 years the bacteriolytic enzymes have excited much intereset as useful tools for elucidating the structure of the bacterial wall peptidoglycans (for reviews see Strominger and Ghuysen, 1967; Ghuysen, 1968). The last few years have seen a new view for the lytic enzymes as factors possibly involved in wall biosynthesis, regulation of Non standard abbreviations: DCIP: 2,6-dichlorophenol-indophenol; SA endo- peptidase: a lyric endopeptidase which lyses Staphylococcus aureus cell walls liberat- ing NH 2 groups of glycine: l~ 1 or "32" enzymes: endo-N-acety]-muramyl glycan hydrolases from Streptomyces albus G; Dap: diaminopimelic acid.