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Voltage-gated ion channels in bacteria
Some bacteria have voltage-gated ion channels, just as higher organisms do, according to a team of researchers led by author. Although their function is unknown in bacteria, these channels in other organisms produce the electrical signals that nerve cells need for learning, memory, movement, and sensation. The simpler channel that the researchers have identified in Bacillus halodurans should be easier to produce in large amounts and to crystallize than previously known channels have been, making it potentially more amenable to structure determination using methods like X-ray crystallography. Already the new channel has revealed some surprises: Studies of earlier voltage-gated channels had led scientists to think that the channels needed to be made of four different protein chains in order to be asymmetric enough to distinguish between different types of cations. The new channel, however, appears to be composed of four identical protein subunits, yet it is very selective for Na+ ions. The fact that it selects for Na+ is also a surprise, since the channel is lined with glutamic and aspartic acid residues, previously thought to characterize channels that select for Ca2+ ions.
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