Dynamic properties of membrane proteins: reversible insertion into membrane vesicles of a colicin E1 channel-forming peptide.
AUTOR(ES)
Xu, S
RESUMO
The binding of colicin E1 and its COOH-terminal channel-forming peptides to artificial membrane vesicles has an optimum at acidic pH values. The Mr 18,000 thermolytic peptide inserted into membrane vesicles at pH 4.0 has a limited accessibility to exogenous protease. It is converted by trypsin cleavage after Lys-381 and Lys-382 to a lower Mr 14,000 peptide. However, when the pH of a vesicle suspension to which peptide has been bound at pH 4.0 is shifted to 6.0, the accessibility to protease increased greatly. This was shown (i) by the large decrease in the amount of Mr 14,000 or Mr 18,000 peptide after the pH 4----6 shift and treatment with trypsin or Pronase, consistent with (ii) a previously observed decrease in membrane-bound radiolabeled peptide after protease treatment. (iii) When a photoactivable nitrene-generating phospholipid probe was used to label the colicin peptide inserted into the bilayer, the extent of labeling decreased by a factor of 3 when the pH was shifted from 4.0 to 6.5. (iv) Colicin peptide added to vesicles at pH 4.0 can "hop" to other vesicles if the pH and ionic strength of donor vesicles are successively increased. It is proposed that deprotonation of acidic residues in contact with the hydrophobic bilayer or the membrane surface destabilizes the inserted channel and causes it to be extruded from the membrane. The pH-dependent extrusion of the inserted colicin channel provides an example of dynamic properties of an intrinsic membrane protein.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=282225Documentos Relacionados
- Channel-forming properties of cecropins and related model compounds incorporated into planar lipid membranes.
- Crystal structure of the channel-forming polypeptide antiamoebin in a membrane-mimetic environment
- Cytolytic and ion channel-forming properties of the N terminus of lymphocyte perforin.
- The Cell Wall of the Pathogenic Bacterium Rhodococcus equi Contains Two Channel-Forming Proteins with Different Properties
- Structural homology of complement protein C6 with other channel-forming proteins of complement.