The number and nature of the peptide-transport systems of Escherichia coli: characterization of specific transport mutants

1980 ◽  
Vol 8 (6) ◽  
pp. 704-705 ◽  
Author(s):  
ROBERT A. ALVES ◽  
JOHN W. PAYNE
Keyword(s):  
Escherichia Coli ◽  
Peptide Transport ◽  
Transport Systems ◽  
Specific Transport ◽  
Transport Mutants

Characterization of two peptide-transport systems in Streptococcus faecalis

1980 ◽  
Vol 8 (6) ◽  
pp. 705-706 ◽  
Author(s):  
TIMOTHY M. NISBET ◽  
JOHN W. PAYNE
Keyword(s):  
Peptide Transport ◽  
Transport Systems ◽  
Streptococcus Faecalis

Molecular characterization of the proU loci of Salmonella typhimurium and Escherichia coli encoding osmoregulated glycine betaine transport systems

1989 ◽  
Vol 3 (8) ◽  
pp. 1025-1038 ◽  
Author(s):  
D. A. Stirling ◽  
C. S. J. Hulton ◽  
L. Waddell ◽  
S. F. Park ◽  
G. S. A. B. Stewart ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Salmonella Typhimurium ◽  
Molecular Characterization ◽  
Glycine Betaine ◽  
Transport Systems

scholarly journals Cation transport in Escherichia coli. VIII. Potassium transport mutants.

1976 ◽  
Vol 67 (3) ◽  
pp. 325-341 ◽  
Author(s):  
D B Rhoads ◽  
F B Waters ◽  
W Epstein
Keyword(s):  
Escherichia Coli ◽  
Transport Systems ◽  
K Uptake ◽  
Low Concentrations ◽  
Transport Mutants ◽  
High Concentrations ◽  
K Concentration ◽  
Independent Path ◽  
Kinetics Of Uptake ◽  
K 12

Analysis of K transport mutants indicates the existence of four separate K uptake systems in Escherichia coli K-12. A high affinity system called Kdp has a Km of 2 muM, and Vmax at 37 degrees C of 150 mumol/g min. This system is repressed by growth in high concentrations of K. Two constitutive systems, TrkA and TrkD, have Km's of 1.5 and 0.5 mM and Vmax's of 550 and 40 at 37 and 30 degrees C, respectively. Mutants lacking all three of these saturable systems take up K slowly by a process, called TrkF, whose rate of transport is linearly dependent on K concentration up to 105 mM. On the whole, each of these systems appears to function as an independent path for K uptake since the kinetics of uptake when two are present is the sum of each operating alone. This is not true for strains having both the TrkD and Kdp systems, where presence of the latter results in K uptake which saturates at a K concentration well below 0.1 mM. This result indicates some interaction between these systems so that uptake now has the affinity characteristic of the Kdp system. All transport systems are able to extrude Na during K uptake. The measurements of cell Na suggest that growing cells of E. coli have very low concentrations of Na, considerably lower than indicated by earlier studies.

Approaches used to examine the mechanism and regulation of hexose transport in rat myoblasts

1986 ◽  
Vol 64 (11) ◽  
pp. 1081-1091 ◽  
Author(s):  
Tony D'Amore ◽  
Theodore C. Y. Lo
Keyword(s):  
Transport System ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Hexose Transport ◽  
Plasma Membrane Vesicles ◽  
Diffusion Type ◽  
High Affinity ◽  
Isolation And Characterization ◽  
Transport Mutants

This review discusses some of the approaches and general criteria that we have used to examine the properties of the hexose transport system in undifferentiated L6 rat myoblasts. These approaches include studying the kinetics of hexose transport in whole cells and plasma membrane vesicles, the effects of various inhibitors on hexose transport, the isolation and characterization of hexose transport mutants, and the use of cytochalasin B (CB) to identify the transport component(s). Transport kinetics indicated that two transport systems are present in these cells. 2-Deoxy-D-glucose is transported primarily by the high affinity system, whereas 3-O-methyl-D-glucose is transported by the low affinity system. Furthermore, these two transport systems are inactivated to different extents by CB. CB has a higher binding affinity for the low affinity hexose transport system. The inhibitory effect of various hexose analogues also revealed the presence of two hexose transport systems. The effects of various ionophores and energy uncouplers on hexose transport suggest that the high affinity system is an active transport process, whereas the low affinity system is of the facilitated diffusion type. The high affinity system is also sensitive to sulfhydryl reagents, whereas the low affinity system is not. Further evidence for the presence of two transport systems comes from the characterization of hexose transport mutants. Two of the mutants isolated are shown to be defective in the high affinity transport system, but not in the low affinity transport system. These mutants are also defective in the CB low affinity binding site. Based on our results a tentative working model for hexose transport in L6 rat myoblasts is presented.

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