Amino acid transporters mutants

In contrast, less effort has apparently been directed to the transport of xenobiotics, and there is an intrinsic difficulty that in contrast to organisms that utilize carbohydrates or amino acids, suitable mutants defective in the metabolism of the substrate may not be available. This limitation makes it impossible to determine directly whether active transport is involved. Although the genes encoding permeases have been described quite frequently, details of their mechanisms have been less well documented ... 

Aiba A, Chen C, Herrup K, et al (1994) Reduced hippocampal long-term potentiation and context-specific deficit in associative learning in mGluRl mutant mice. Cell 79 365-375 Amara SG, Fontana ACK (2002) Excitatory amino acid transporters keeping up with glutamate. Neimochem Int 41 313-318... 

Mutants of E. coli lacking the amine-containing lipids PE (psdA null) or PS and PE (pssA null) are viable when grown in the presence of millimolar concentrations of Ca ", Mg, and Sr but have a complex mixture of defects in cell division, growth rate, outer membrane barrier function, energy metabolism, assembly of membrane proteins, and sugar and amino acid transport [1]. 

Fig. 8. Mutagenesis of the predicted ATP binding site. ATP is shown in proximity to amino acids in four loops predicted to form the ATP binding site in the nucleotide binding domain [49,134] and a fifth loop representing the phosphorylation site at Asp351 [97], Mutations and the corresponding Ca transport activity of the mutants relative to wild-type are indicated. From Clarke et al. [103).

Halorhodopsiti. In addition to bacteriorhodopsin there are three other retinal-containing proteins in membranes of halobacteria. From mutant strains lacking bacteriorhodopsin the second protein, halorhodopsin, has been isolated. It acts as a light-driven chloride ion pump, transporting Cl from outside to inside. Potassium ions follow, and the pump provides a means for these bacteria to accumulate KC1 to balance the high external osmotic pressure of the environment in which they live.578 The amino acid sequences of halorhodopsins from several species are very similar to those of bacteriorhodopsin as is the three-dimensional structure.589 However, the important proton-carrying residues D85 and D96 of bacteriorhodopsin are replaced by threonine and alanine, respectively, in halorhodopsin.590 Halorhodopsin (hR)... 

---