Evidence for high affinity binding-protein dependent transport systems in gram-positive bacteria and in Mycoplasma |
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Authors: | E Gilson G Alloing T Schmidt J P Claverys R Dudler M Hofnung |
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Affiliation: | Unité de Programmation Moléculaire et Toxicologie Génétique, CNRS UA271, INSERM U163, Institut Pasteur, Paris, France. |
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Abstract: | Gram-negative bacteria are surrounded by two membranes. In these bacteria, a class of high affinity transport systems for concentrating substrates from the medium into the cell, involves a binding protein located between the outer and inner membranes, in the periplasmic region. These 'periplasmic binding-proteins' are thought to bind the substrate in the vicinity of the inner membrane, and to transfer it to a complex of inner membrane proteins for concentration into the cytoplasm. We report evidence leading us to propose that a Gram-positive bacterium, Streptococcus pneumoniae, and a mycoplasma, Mycoplasma hyorhinis, which are surrounded by a single membrane and have therefore no periplasmic region, possess an equivalent to the high affinity periplasmic binding-protein dependent transport systems, i.e. extra-cytoplasmic binding lipoprotein dependent transport systems. The 'binding lipoproteins' would be maintained at proximity of the inner membrane by insertion of their N-terminal glyceride-cysteine into this membrane. |
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