Spectrin is the protein of membrane skeleton of red blood cell which forms elongated tetramer made up of 2 aIbI heterodimers linked head-to-head, and attached at their distal ends to junctional complexes. This protein, linked to the membrane through interactions with transmembrane proteins, can also bind to the aminophospholipids of the inner membrane leaflet, as has been established and described by many authors, and this interaction can play an important role in stabilizing the erythrocyte membrane. Main binding site engaged in this interaction was identified as fragment of b-spectrin ankyrin binding domain. Spectrin consists largely of series of homologous repeating 106 amino acid units, each of them form triple helical coiled-coil bundle with the helices marked as A, B, and C, of which A and C are parallel and B is antiparallel. At room temperature spectrins and their mutants show 45-75% of a helix, as measured by circular dichroism spectra, and seem to be highly folded.

We attempted to answer the question; how termal unfolding and exposing of hydrophobic amino acids residues affect spectrin-lipids interaction?

We report the results of monolayer experiments carried on PE/PC 6/4 phospholipid mixtures at pH 7.5, that are optimal for spectrin-phospholipid interaction. The changes in monolayer surface pressure after adding native folded and heat-denaturated (70^oC, 30 min.) protein to the subphase were tested. We used spectrin and fodrin b-subunit ankyrin binding domain and a series of their truncated mutants.

We have observed an increase in the surface pressure of the monolayer for all used non-denaturated proteins, that indicate the penetration of monolayer by spectrins and their mutants. In contrast, heat-treated proteins induce a much smaller increase of surface pressure than observed in case of native proteins or even a decrease in surface pressure was observed. It seems that unfolding of spectrins and their b-spectrin ankyrin binding domain fragments markedly decreases the ability of studied proteins to penetrate the phospholipid monolayer. Therefore these results indicate that the ability to penetrate phospholipid monolayer by spectrins is a property of native proteins not a result of unfolding and denaturation.

Supported by KBN grant no. 2P04A 021 27.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/10817 must be provided.