Bacteria sugar transport

Transport systems can be described in a functional sense according to the number of molecules moved and the direction of movement (Figure 41-10) or according to whether movement is toward or away from equilibrium. A uniport system moves one type of molecule bidirectionally. In cotransport systems, the transfer of one solute depends upon the stoichiometric simultaneous or sequential transfer of another solute. A symport moves these solutes in the same direction. Examples are the proton-sugar transporter in bacteria and the Na+ -sugar transporters (for glucose and certain other sugars) and Na -amino acid transporters in mammalian cells. Antiport systems move two molecules in opposite directions (eg, Na in and Ca out). 

The system can be applied for examination of control mechanisms of metabolic coupled enzyme systems, such as the sugar transport system in bacteria. 

A brief description of sugar transport in bacteria and mammals is given principally to illustrate general principles and to outline the diversity of the processes which have evolved, particularly in mammals. The selection of material for this section is of necessity, therefore, somewhat arbitrary, and more comprehensive surveys of sugar transport may be found in several recent reviews (I, 2, 3, 4, 5, 6, 7, 8, 9,10, II, 12,13, 14). 

The definition on a molecular basis of these different sugar transport systems has not progressed to the same extent as with bacteria, partly because of the greater convenience of bacteria as experimental organisms, and also because of the greater complexity of the mammalian systems themselves. 

Figure 1 Examples of several bacterial membrane proteins. The outer membrane (OM) of Gram-negative bacteria contains exclusively fS-barrel proteins, and three examples are shown BtuB (PDB ID 1NQF), which is the 22 p-stranded TonB-dependent active transporter for vitamin B 2/ th LamB or maltoporin trimer (PDB ID 1AF6), which is the 18 p-stranded passive sugar transporter and OmpA (PDB ID 1BXW), which is an 8 p-stranded protein that provides structural support for the OM. Proteins in the cytoplasmic membrane (CM) are helical, and three examples are shown the potassium channel KcsA (PDB ID 1BL8), which is a tetramer Sec YEG (PDB ID 1RH5), which forms the protein transport channel in Methanococcus and BtuCD (PDB ID ...

A.R. Walmsley, M.P. Barrett, F. Bringaud, and GW. Gould. 1998. Sugar transporters from bacteria, parasites and mammals Structure-activity relationships Trends Biochem. Sci. 23 476-480. (PubMed)... 

R181 O. M. M. Bouvet and M.-N. Rager, Sugar Transport and Metabolism in Fermentative Bacteria , p. 349... 

Walmsley, A. R., Barrett, M. P., Bringaud, P ., and Gould, Cj. W. 1998. Sugar transporters from bacteria, parasites and mammals Structure activity relationships. Trends Biochem. Sci. 23 476 480. Maes, U., Zeelen, J. R, Thanki, N.. Beaucamp, N., Alvarez. M., Thi. M H., Backmann, J., Martial, J. A., Wyns, L., Jaenicke, R., and Wierenga, R. K. 1999. Fhe crystal structure of triosephosphate iso-merase (TIM) from Ihermotogn maritima A comparative thermostability structural analysi.s of ten different TIM stmetures. Proteins 37 441-4. S3. 

Figure 36.3 The active transport and metabolism of sugars by bacteria. PTS, membrane-associated phosphotransferase sugar-transport system PEP, phosphoenolpyruvate F , sites of fluoride inhibition...

Stiles ME, Holzapfel WH (1997) Lactic acid bacteria of foods and their current taxonomy. Int J Food Microbiol 36 1-29 Svetoch EA, Stern NJ (2010) Bacteriocins to control Campylobacter spp. in poultry - a review. Poult Sci 89 1763-1768 Thompson J (1988) Lactic acid bacteria model systems for in vivo studies of sugar transport and metabolism in gram-positive organisms. Biochimie 70 325-336... 

Walmsiey, A.R. Barrett, M.P. Bringaud, F. Gould, G.W. Sugar Transporters from Bacteria, Parasites and Mammals Structure-activity Relationships. TIBS 1998, 23, 476-481. 

The gradients of H, Na, and other cations and anions established by ATPases and other energy sources can be used for secondary active transport of various substrates. The best-understood systems use Na or gradients to transport amino acids and sugars in certain cells. Many of these systems operate as symports, with the ion and the transported amino acid or sugar moving in the same direction (that is, into the cell). In antiport processes, the ion and the other transported species move in opposite directions. (For example, the anion transporter of erythrocytes is an antiport.) Proton symport proteins are used by E. coU and other bacteria to accumulate lactose, arabinose, ribose, and a variety of amino acids. E. coli also possesses Na -symport systems for melibiose as well as for glutamate and other amino acids. 

The determination of the structure of the iron transporter, ferric-binding, protein (hFBP)t from Haemophilus influenzae (Bruns et ah, 1997) at 0.16 nm resolution shows that it is a member of the transferrin superfamily, which includes both the transferrins and a number of periplasmic binding proteins (PBP). The PBPs transport a wide variety of nutrients, including sugars, amino acids and ions, across the periplasm from the outer to the inner (plasma) membrane in bacteria (see Chapter 3). Iron binding by transferrins (see below) requires concomitant binding of a carbonate anion, which is located at the N-terminus of a helix. This corresponds to the site at which the anions are specifically bound in the bacterial periplasmic sulfate- and... 

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