3.4. carriers. 1.carriers exhibit michaelis-menten kinetics that indicate conformational changes...
TRANSCRIPT
![Page 1: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/1.jpg)
3.4. Carriers
![Page 2: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/2.jpg)
1. Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport.
Carriers exhibit saturation kinetics.
![Page 3: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/3.jpg)
Carriers undergo conformational changes during transport (ex, The activity of carrier C)
![Page 4: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/4.jpg)
2. Carriers translocate a wide variety of inorganic and small organic solutes with high specificity.
1) Inorganic nutrients: NH4+, NO3-, Pi, K+, SO42-, Cl-
2) Organic solutes: sugars, amino acids, purine and pyrimidine bases
![Page 5: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/5.jpg)
Functions of carriers
1. At plasma membrane, - nutrient uptake - the mobilization and storage of metabolites.
2. At endomembrane, - sequestration of ions (Na+, Ca2+, Mg2+, No3-, sugars, aa)
![Page 6: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/6.jpg)
3. Most plant carriers are energized by coupling to pmf.
![Page 7: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/7.jpg)
4. Molecular identification of carriers defines them as members of the major facilitator superfamily
Functional analysis
1. By yeast complementation
2. By protein expression in Oocytes
![Page 8: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/8.jpg)
Observation of plant carriers expressed in heterologous systems can provide into carrier function
![Page 9: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/9.jpg)
Structural model illustrating the orientation of a generalized carrier in a membrane
![Page 10: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/10.jpg)
Localization of the sucrose transporter SUC2 to companion cells of the phloem
A. Immunofluorescent localization of SUC2 in Arabidopsis stems.
B. Same section as in A but viewed with transmitted light.
P: phloem X: xylem
![Page 11: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/11.jpg)
Localization of the sucrose transporter SUT1 to sieve elements
A. Immunofluorescent localization of SUT1 in a longitudinal section of a potato stems.
B. Silver-enhanced Immunogold localization of SUT1 in cross-section of a potato petiole
sp: sieve plate n: nucleus cc: companion cells
![Page 12: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/12.jpg)
6. Regulation of carrier activity
1) By transcriptional control
2) By post-translational control
![Page 13: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/13.jpg)
Low K+: 40 uM,
High K+: 2 mM
Different transcription of AtKUP2 and AtKUP3
![Page 14: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/14.jpg)
7. In some cases, ion-coupled solute transport
involves Na+ rather than H+
1. Na+ symport have been found.
2. Na+coupling of K+ transport has been proved by a wheat cDNA
a. Uptake of NO3- and some amino acids is Na+-dependent
b. uptake of K+ at micromolar concentration is also Na+-dependent
![Page 15: 3.4. Carriers. 1.Carriers exhibit Michaelis-Menten kinetics that indicate conformational changes during transport. Carriers exhibit saturation kinetics](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f495503460f94c6a8a4/html5/thumbnails/15.jpg)
Acetabularia, a marine algae