Plasma membranes bacterial

Assume that the free energy change, AG, associated with the movement of one mole of protons from the outside to the inside of a bacterial cell is —23 kJ/mol and 3 must cross the bacterial plasma membrane per ATP formed by the bacterial FjEo-ATP synthase. ATP synthesis thus takes place by the coupled process ... 

Bacteria normally harbour a single, circular chromosome that tends to be tethered to the bacterial plasma membrane and tends to have few if any closely associated proteins. Many bacteria also contain extra-chromosomal DNA in the form of plasmids, as will be discussed later. Eukaryotes (plants, animals and yeasts) posses multiple linear chromosomes contained within a cell nucleus, and these chromosomes are normally closely associated with proteins termed histones (the pro-tein-DNA complex is termed chromatin). Eukaryotes also invariably possess DNA sequences within mitochondria and in chloroplasts in plants. The (usually circular) DNA molecules are much... 

F0Fi ATPase/ATP synthase of mitochondrial inner 19-58 membrane, chloroplast thylakoid, and bacterial plasma membrane... 

The timing of replication initiation is affected by DNA methylation and interactions with the bacterial plasma membrane. The oriC DNA is methylated by the Dam methylase (Table 25-3), which methylates the Na position of adenine within the palindromic sequence (5 )GATC. (Dam is not a biochemical expletive it stands for DNA adenine methylation.) The oriC region of E. coli is highly enriched in GATC sequences—it has 11 of them in its 245 bp, whereas the average frequency of GATC in the E. coli chromosome as a whole is 1 in 256 bp. 

Replication of the E. coli chromosome involves many enzymes and protein factors organized in replication factories, in which template DNA is spooled through two replisomes tethered to the bacterial plasma membrane. 

Not all proton pumps are driven by electron transport. ATP synthase is reversible, and if Ap is low, hydrolysis of ATP can pump protons out of mitochondria or across bacterial plasma membranes.268 Cells of Streptococcus faecalb, which have no respiratory chain... 

In green plants and algae, photosynthesis takes place in chloroplasts. The light reactions occur in the thylakoid membranes and the dark reactions take place in the stroma. In photosynthetic bacteria the light reactions take place in the bacterial plasma membrane, or in invaginations of it (chromatophores). 

Because cholesterol contains an -OH group, it is amphipathic. It controls membrane fluidity in mammals by inhibiting the ordering of fatty acid side chains, but it is absent from bacterial plasma membranes. 

Complexes of the two polymers, isolated from bacterial plasma membranes or prepared from synthetic polymers, form voltage-dependent, Ca2+-selective channels in planar lipid bilayers that are selective for divalent over monovalent cations, permeant for Ca2+, Sr2+... 

R. N. Reusch and H. L. Sadoff (1988). Putative structure and functions of poly-beta-hydroxybutirate/calcium polyphosphate channel in bacterial plasma membranes, Proc. Natl. 

Dalbey, R., and Robinson, C. (1999). Protein translocation into and across the bacterial plasma membrane and the plant thylakoid membrane. TrendsBiochem. Set. 24, 17-22. 

In order to maintain a A/1h+ across a membrane, and to ensure that it is used for the synthesis of ATP and not dissipated by leakage, the membrane must be closed and not leaky to protons. From the rate at which a pH gradient across the membrane decayed, it was shown that the effective proton conductance of the mitochondrial inner membrane [8], bacterial plasma membrane [9], and chloroplast thylakoid membrane [10] have a value of only some 0.5 jttS2/cm, or a million-fold less than the aqueous phases on either side. 

ATP synthase. An enzyme complex that forms ATP from ADP and phosphate during oxidative phosphorylation in the inner mitochondrial membrane or the bacterial plasma membrane, and during photophosphorylation in chloroplasts. Uses aproton gradient to chemiosmotically drive the synthesis. 

ATP synthase, FoFi(8) H+ gradient Multiple subunits forming Fo and Fi particles Inner mitochondrial membrane, thylakoid membrane, bacterial plasma membrane Rotation of y subunit leading to ATP synthesis... 

Bacterial plasma membranes (amino acid, sugar, and peptide transporters)... 

The structures of F class and V class ion pumps are sIm liar to one another but unrelated to and more complicated than P-class pumps. F- and V-class pumps contain several different transmembrane and cytosolic subunits. All known V and F pumps transport only protons. In a process that does not Involve a phosphoprotein Intermediate. V-class pumps generally function to maintain the low pH of plant vacuoles and of lysosomes and other acidic vesicles In animal cells by pumping protons from the cytosolic to the exoplasmic face of the membrane against a proton electrochemical gradient. F-class pumps are found In bacterial plasma membranes and In mitochondria and chloroplasts. In contrast to V pumps, they generally function to power the synthesis of ATP from ADP and Pj by movement of protons from the exoplasmic to the cytosolic face of the membrane down the proton electrochemical gradient. Because of their Importance In ATP synthesis in chloroplasts and mitochondria, F-class proton pumps, commonly called ATP synthases, are treated separately In Chapter 8. 

Bacterial plasma membrane becomes inner membrane of mitochondrion... 

Bacterial Plasma-Membrane Proteins Catalyze Electron Transport and Coupled ATP Synthesis... 

Although bacteria lack any internal membranes, aerobic bacteria nonetheless carry out oxidative phosphorylation by the same processes that occur in eukaryotic mitochondria. Enzymes that catalyze the reactions of both the glycolytic pathway and the citric acid cycle are present in the cytosol of bacteria enzymes that oxidize NADFI to NAD and transfer the electrons to the ultimate acceptor O2 are localized to the bacterial plasma membrane. 

Stage 3 Synthesis of ATP Protons move down their concentration gradient from the thylakold lumen to the stroma through the FqFi complex (ATP synthase), which couples proton movement to the synthesis of ATP from ADP and Pj. The mechanism whereby chloroplast FqFi harnesses the proton-motive force to synthesize ATP is identical with that used by ATP synthase in the inner mitochondrial membrane and bacterial plasma membrane (see Figures 8-24 and 8-26). 

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