Voltage-dependent K+ (Kv) channels conduct K+ ions across the cell membrane in response to changes in the membrane voltage. The channels contain voltage sensors that allow them to open and close their ion conduction pore over narrow voltage ranges. The structure of the voltage-dependent K+ channel Kv1.2 reveals that the voltage sensors are essentially independent domains inside the membrane and suggests how they perform mechanical work to open and close the pore.
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Ras and many other oncogenic proteins undergo a series of post-translational modifications that are initiated by the attachment of an isoprenoid lipid. These processing steps are crucial for the proper functioning of the modified proteins and affect the transforming activity of oncogenic variants of Ras. The lipid group is attached to a cysteine residue that is four residues away from the C-terminus of the protein substrate by one of two closely related prenyltransferase enzymes: protein farnesyltransferase or protein genanylgeranyltransferase.
