A model for ionic and hydrophobic interactions and hydrogen-bonding in sodium dodecyl sulfate-protein complexes
Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology(1986)
摘要
We propose a new hypothetical model for the structure of complexes between sodium dodecyl sulfate and proteins as described below: the detergent forms a flexible capped cylindrical micelle around which the hydrophilic segments of the polypeptide are helically wound. These polypeptide segments are attached by hydrogen bonds from the nitrogens of the peptide bonds to the sulfate oxygens of the detergent molecules. Cationic amino acid side-chains can also form ionic bonds with the sulfate groups. When the latter occurs the polypeptide assumes an α-helical conformation at the surface of the detergent cylinder in accordance with interpretations of circular dichroism measurements (Mattice, W.L. Riser, J.M. and Clark, D.S. (1976) Biochemistry 15, 4264–4272). An essentially regular arrangement of one hydrogen bond per peptide bond and two per dodecyl sulfate monomer is consistent with the known binding ratio of approximately one detergent molecule per two amino acid residues and with the proportionality between the polypeptide molecular mass or the number of residues and the length of the complex (Reynolds, J.A. and Tanford, C. (1970) J. Biol. Chem. 245, 5161–5165).The hydrogen-bonded structure of our model also agrees with the finding that dodecyl sulfate associates much more readily with proteins than does tetradecyltrimethylammonium chloride (Nozaki, Y., Reynolds, J.A. and Tanford, C. (1974) J. Biol. Chem. 249, 4452–4459). The axial length of the structure we propose can be estimated at approximately 0.6 Å per amino acid residue. Hydrophobic polypeptide segments, including membrane-spanning α-helices of integral membrane proteins, can be accommodated in the interior of the elongated dodecyl sulfate micelle. Therefore, not only water-soluble proteins but also some integral membrane proteins may form the proposed type of complex. In the case of glycosylated membrane proteins the sugar moieties will protrude from the surface of the rod-shaped complex. We have named our model ‘the flexible helix’.
更多查看译文
关键词
Sodium dodecyl sulfate protein complex,Membrane protein,Dodecyl sulfate-polypeptide hydrogen-bonding,Detergent-protein interaction,Structural model
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络