Evidence for high affinity binding-protein dependent transport systems in gram-positive bacteria and in Mycoplasma.
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.
Gilson
E
E
Unité de Programmation Moléculaire et Toxicologie Génétique, CNRS UA271, INSERM U163, Institut Pasteur, Paris, France.
Alloing
G
G
Schmidt
T
T
Claverys
J P
JP
Dudler
R
R
Hofnung
M
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000502:physiology*; D001692:Biological Transport; D006094:Gram-Positive Bacteria / Q000502:physiology*; D008074:Lipoproteins / Q000502:physiology; D008320:Maltose / Q000378:metabolism; D008565:Membrane Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D009174:Mycoplasma / Q000502:physiology*; D009842:Oligopeptides / Q000378:metabolism
D001426:Bacterial Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; D009842:Oligopeptides; D008320:Maltose