Chapter 11. Membranes: Transport Part 2. Learning Goals. To KNOW: mechanisms of molecular transport in and out of cells. transport kinetics (really easy after Chapter 6!)
Chapter 11 Membranes: Transport Part 2
Learning Goals • To KNOW: • mechanisms of molecular transport in and out of cells. • transport kinetics (really easy after Chapter 6!) • specific transporters: Ca++ transporter, Na+/K+ transporter, glucose transport in gut epithelial cells, P,V and F-type ATPases, lactose transport in bacteria • aquaporins
Energetics of Diffusion Transport EOC Problem 15 is all about tryptophan and indole permeability, review their structure (Chapter 3) or you already know it !!
Polar Groups Define the Transporter Pore EOC Problem 11 deals with evidence on the location of membrane proteins. A good class activity.
Transport Kinetics vo = Vmax [Sout] / (Kt + [Sout]) ktis the same as kcat…. and Ktis Km of transport
Insulin Increases Number of Glucose Transporters Related to this is membrane self-sealing: Check out EOC Problem 12
Secondary Transporters Secondary Transporters = use a chemical gradient + electrical gradient.
S1 is usually H+ or Na+ Therefore Outside Cell Membrane (Na+) or Mitochondria Membrane (H+) there is: high concentration of S1and lower in the cytoplasm or mitochondrial matrix. On the outside: higher chemical conc. + electrical charge …….these are 2 energetic components. This is called either the Proton Motive Force or Sodium Motive Force
Inhibitor of P-type ATPases which become Phosphorylated in the Transport Cycle
P-type Na+/K+ ATPase Maintains the Na+ - K+ disequilibrium If you add up just the sodium and potassium concentrations…it doesn’t seem right, but it is because the concentrations of Cl-, Mg++, Ca++ and all the other weak acids are all part of the overall electrochemical-gradient.
Ouabain Binds to the Open - Outside form of Na+K+ATPase..and hold it there. Arrow Poison
ABC Transporters in E. coli Nucleotide Binding Domains Lipid-a Flippase Vit-B12 Transporter
CFTR (Chloride Transporter) Cystic Fibrosis Transmembrane conductance Regulator
Cystic Fibrosis Patients Can’t Clear Bacteria in Bronchia-Trachea Cystic Fibrosis – Research at FIU in Dr. Kalai Mathee’s Lab
CFTR In Action See Box 11-2 Page 415 For More
Lactose Transporter in Two Forms 12 Transmembrane Helices Arg and Glu in Green, Lactose in Red
How Are Transporters Regulated? 1st Crystal Structure of the E. coli Methionine ABC Transporter Fig. 1. (A) ABC transporter MetNI consists of four subunits: two membrane-spanning MetI subunits (green and pink) and two MetN ABC subunits (purple and tan) Structure B is A in a 90o Turn TMD – transmembrane domain, NBD – Nucleotide binding domain, C-2 Methionine binding domain
C-2 Domain of Met-Transporter Methoinine – gold structures. When bound, Met inhibits the NDB as an ATPase, Ki ~ 30 µM Ref: Kadaba, Kaiser, Johnson, Lee and Rees. 2008. The high affinity E. coli methionine ABC transporter: structure and allosteric regulation. SCIENCE 231:250-253
Things to Know Membrane transport kinetics: KT and kt Amino acids in transmembrane domain of transporters. Primary and Secondary Transporters. Transporters as motors. PMF. Cell location of transporters: intestinal cell model. Transporter regulation Aquaporins EOC Problems : 10-13, 15, 16, 22 .
Model for EOC Problem 22 Fill in the Amino Acids with Single Letter Code: What does it tell you? Val-Asp-Arg-Val-Phe-Ser-Asn-Val-Cys-Thr-His-Leu-Lys-Thr-Leu-Gln-Asp-Lys