Structure-function relationships for a voltage-dependent ion channel: properties of COOH-terminal fragments of colicin E1.
AUTOR(ES)
Cleveland, M V
RESUMO
The effects on planar lipid bilayer membranes of carboxyl-terminal fragments derived from the bacteriocin colicin E1 by either proteolysis or CNBr cleavage are indistinguishable from those of the voltage-dependent parent colicin molecule. An upper limit to the length of the COOH-terminal peptide required for channel formation is 152 amino acid residues from the COOH-terminal end, as indicated by the CNBr fragment. In addition, use of carboxypeptidase shows that the COOH-terminal end of the molecule remains on the side of the membrane to which it was added. COOH-terminal peptides of colicin E1 spontaneously associate with oil or hexane droplets in an aqueous system and remain at the interface between the two phases to a significantly greater degree than other colicin E1 fragments or cytochrome c. These results, together with the amino acid sequence, suggest a model wherein the colicin E1 channel is formed first by spontaneous attachment to a membrane of an alpha-helical hairpin centered at a 35-residue hydrophobic region near the COOH-terminal end. Application of a potential of the correct polarity then facilitates a major conformational change in the protein, allowing insertion of the remainder of the COOH-terminal end to form the open channel.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=394119Documentos Relacionados
- Site-directed mutagenesis of the COOH-terminal region of colicin A: effect on secretion and voltage-dependent channel activity.
- Localization of the immunity protein-reactive domain in unmodified and chemically modified COOH-terminal peptides of colicin E1.
- Structure-function relationships of protein polysaccharide complexes: specific ion-binding properties.
- Translocation of a functional protein by a voltage-dependent ion channel
- Voltage-dependent inactivation of a calcium channel.