Shaker mutation

The first voltage-gated potassium channel to be identified was the gene encoding the Shaker mutation in the fruit fly Drosophila. Figure 9.3 presents the hrst pictures of the tetrameric Shaker K+ channel with... 

Fig. 3. (A) Model of the proposed pore forming part of K channel subunits. Segments S5 and S6 are possibly membrane-spanning helices. The helices are connected by a hydrophobic segment H5 which may be tucked into the lipid bilayer [48]. H5 is flanked by two proline residues P. Adjacent to these proline residues are amino acid side chains ( ) important for external TEA binding [45,46]. Approximately halfway between these two proline residues are amino acid side chains ( ) affecting internal TEA binding [46,47] and K channel selectivity [48]. (B) Mutations are indicated which affect in Shaker channels external TEA (TEAe) or internal TEA (TEA,) binding. Concentrations of TEA for half block of the wild-type and mutant K channels are given at the right-hand side of the corresponding sequence. Data have been compiled from [45-47].

Two other myosin types have been implicated in hearing and vestibular function [62]. The defect in the Snell s waltzer mouse was found to be a mutation in a myosin VI gene that produces degeneration of the cochlea and vestibular apparatus. Myosin VI is localized to the cuticular plate of the hair cell under stereocilia. Similarly, mutations in a myosin VII gene are responsible for the shaker-1 mouse and several human genetic deafness disorders. This myosin, myosin Vila, is found in a band near the base of the stereocilia distinct from distributions of myosin ip and myosin VI. 

A. vinelandii UWD and W. eutropha were grown in a two-step process, employing a pre-culture and a polymer medium. For PEG and DEG modulated fermentation, A. vinelandii UWD was used. After 48 h of growth, 10 vol.% of the pre-culture were used as inoculum for the polymer medium, which was harvested after 24 h (12). Both media were amended with 2.0 wt % of the respective PEGs. It is noteworthy that A. vinelandii UWD must be grown in the presence of 20 mg/L rifampicin, in order to prevent the back mutation of the engineered strain to the A. vinelandii UW parental strain genotype, which is not resistant to the antibiotic. All fermentation experiments were conducted in a shaker-incubator (New Brunswick Scientific) at 30 °C and 180 rpm. Cells were... 

---